Oak mushroom (Lentinus edodes Sing.) has been used as one of vegetable foods for a long time, because it has particular odour, taste and abundant nutritive material. Its cultivation has been done extensively, but its checmical analysis of the components is curiously limited. It is the purpose of this study to analyse its component chemically and to get basic data in terms of nutrition science. The results are summarized as follows: 1. It was analysed that the total number of amino acid is 17 different kinds, mainly glutamic acid. 2. All the essential amino acids which are lecucine, lysine, threonine, tryptophan, valine, phenylalanine, isoleucine, tyrosine, and methionine were found in this chemical analysis. 3. The seven kinds of vitamins are analysed, which are A(${eta}$-carotene), $B_1$ (thiamin), $B_2$(riboflavin), C(ascorbic acid), E(${alpha}$-tocopherol), Niacin, choline chloride.