Theoretical and empirical studies of life history assume that egg size and number cannot be maximized simultaneously because of a trade-off between them. In many empirical studies, however, only egg size or egg number was examined as a fitness component of the mother. We estimated phenotypic and genetic correlations between egg size and number, and heritabilities of each trait by half-sib analysis in Callosobruchus chinensis (L.) (Coleoptera: Bruchidae). The signs of all genetic correlations between egg size and egg number were negative, but near zero and not significantly different from zero. The result means that no trade-off was found between egg size and egg number, at least in this beetle population. We discuss three reasons (i.e., laboratory adaptation, mutation, and resource acquisition ability) why we did not detect a significant negative genetic correlation between egg size and egg number even when genetic trade-off existed.