Dry powders of amino acids which exhibit great oral meltability and solubility, may be produced by spray drying a hydrous liquid of amino acids to produce a powder of amino acids, where the hydrous liquid of amino acids is prepared into the form of microfine liquid droplets in the presence of trehalose for spray drying, to obtain a powder having a mean particle size of 0.1 .mu.m to 15 .mu.m, as well as granulating and drying during the spray drying or after the spray drying, to obtain a granulated powder having a mean particle size of 20 .mu.m to 1,000 .mu.m.