In producing cordierite glass-ceramics by sintering, following experiments were conducted in order to determine the optimum heat-treatment schedule for high-crystallinity and dense sintered body. The glass composition of 11.67MgO-29.46Al2O3-52.88SiO2-5P2O5-1B2O3 (wt%) was selected on the basis of the early experiment. The 3-step heat treatment schedule was determined by the results of DTA, Dilatometric measurement and high-temperature XRD, where the particle-size-controlled glass powder was used. The degree of densification and the crystallinity were evaluated by the measurement of the bulk density and X-ray scattering intensity. The specimen fired with the optimum conditions showed ${alpha}$-cordierite phase, relative density ∼98%, crystallinity ∼92%, thermal expansion coefficient ∼30${ imes}$10-7/$^{circ}C$, dielectric constant ∼5.5 and resistivity ∼1.0${ imes}$1012 {{{{ OMEGA }}cm, respectively.