The purpose of this paper is to compare the manufacturing process with random covariate using multiple comparison procedure. The methodology that compares each manufacturing process by inspecting the number of nonconforming items out of k-treatment, has serveral limitations and problems according to the method and contect of the analysis. The proper way of analysis, therefore, could be obtained by the multiple comparison procedure of simultaneous confidence region of variance components. Effections that affect a manufactuing process may be predictive of responce to treatments are called covariates. In the study of comparing several treatments, prsense of covariate may bias the estimates of treatment effects.