It is important to discriminate between tuberculosis and tuberculosis-like disease by Mycobacteria other than tuberculosis in the serodiagnosis of tuberculosis. But because common antigens share among Mycobacteria, their antigenicities to human are similar. Therefore degree of cross-reactivity of antibody in the sera of patients with tuberculosis between M. tuberculosis and Mycobacteria other than tuberculosis should be checked to increase the specificity in the serodiagnosis of tuberculosis. The activity levels of IgG antibody in the sera of 106 patients confirmed as active pulmonary tuberculosis and 30 normal healthy control person to the pressate extract antigen (TE, BE, AE, and FE antigen) from M. tuberculosis, M. bovis, M. avium, and M. fortuitum were measured by enzyme-linked immunosorbent assay and the crossreactivity of IgG antibody with mycobacterial species was analysed. The results were as follows; 1. The activity level(O.D. at 492nm) of IgG to TE antigen in sera of patients with pulmonary tuberculosis was $0.228{pm}0.167$ in minimal tuberculosis; moderately advanced, $0.556{pm}0.616$; far advanced, $1.116{pm}0.651$ and $0.315{pm}0.245$ in miliary tuberculosis. 2. The activity level (O.D. at 492nm) of IgG to BE antigen in sera of patients with pulmonary tuberculosis was $0.190{pm}0.162$ in minimal tuberculosis; moderately advanced, $0.337{pm}0.361$; far advanced, $0.713[pm}0.460$ and $0.204{pm}0.162$ in miliary tuberculosis. 3. The activity level (O.D. at 492nm) of IgG to AE antigen in sera of patients with pulmonary tuberculosis was $0.165{pm}0.114$ in minimal tuberculosis; moderately advanced, $0.392{pm}0.494$; far advenced, $0.751{pm}0.512$ and $0.233{pm}0.191$ in miliary tuberculosis. 4. The activity level (O.D. at 492nm) of IgG to FE antigen in sera of patients with pulmonary tuberculosis was $0.280{pm}0.227$ in minimal tuberculosis; moderately advanced, $0.460{pm}0.564$ ; far advanced, $0.845{pm}0.573$ and $0.257{pm}0.103$ in miliary tuberculosis. 5. The activity level (O.D. at 492nm) of IgG in sera of healthy control person was $0.126{pm}0.084$ to TE antigen. $0.105{pm}0.041$ to BE antigen, $0.103{pm}0.052$ to AE antigen, and $0.095{pm}0.061$ to FE antigen. 6. Degree of correlation(r) in activity level of IgG between TE antigen and BE antigen was 0.905 ; between TE antigen and AE antigen, 0.760; between TE antigen and FE antigen, 0.790, and between AE antigen and FE antigen, 0.945. 7. As O.D. above 0.200 was determined positive for the serodiagnosis of pulmonary tuberculosis, the sensitivity and specificity in ELISA using TE antigen were 80% and 87% respectively, whereas in the case of using BE antigen, 66% and 100%; in the case of using AE antigen, 62% and 100%, and in the case of using FE antigen, 72% and 93%, respecitively.