Free amino acids in extracts and total amino acids in hydrolysates of eleven species of edible mushrooms were analyzed by amino acid autoanalyzer (Technicon PNC-1 Type). All these 11 species of mushroom can be repesented for convenience sake as follows. S-1; Agaricus campestris Fr. S-2: Agaricus campestris S-3; Pholiota nameko(I. Ito) S. Ito et Imai S-4; Auricularia auricula-judae(Fr.) $Qu{\acute{e}}l$ S-5; Tremella fuciformis Berk. S-6; Tricholoma matsutake(S. Ito et Imai) Sing. S-7; Pleurotus ostreatus Fr. $Qu{\acute{e}}l$ S-8; Lentinus edodes Berk Sing. S-9; Ramaria botrytis (Pers.) Ricken S-10; Coprinus comatus(Fr.) S.F, Gray S-11; Gyrophora esculenta The results obtained from this study are as follows. 1) 17 kinds of amino acid, including 7 kinds of essential amino acid in human nutrition except tryptophan were identified and quantified. 2) Of all free amino acids contained in mushrooms, glutamic acid is the richest, and then comes Ala, Thr, Pro and Lys in that order. There were no found Cys'and His in S-9;His in S-1; Met and Arg in S-11; Cys and Met in S-5;Pro, Cys, Met, Lys and Arg in S-4. Of all total amino acids which are closely related with nutritional valuation, glutamic acid is the richest, and then comes Asp, Ala, Arg, Leu, Thr, Gly in that order. Especially S-1 and S-2 contain high quantity $o{\acute{i}}$ proline in both free and total amino acids. 3) Cotents of ammonia in extracts of mushrooms in decreasing order in S-1, S-10, S-8, S-2, S-7, S-6, and S-2, S-6, S-8, S-9, S-1 in hydrolysates of mushrooms. 4) Gross Contents of free amino acid in extracts is high in decreasing order in S-10, S-1, S-7, S-6, S-8, and total amino acid in hydrolysates is high in S-10, S-2, S-2, S-8, S-1, S-9, S-6. 5) Besides 17 kinds of amino acid, 5 kinds of unknown amino acid are found in extracts and hydrolysates.