An acid phosphatase with a very high substrate specificity for glucose-1-phosphate was isolated for the first time from mycelia of Pholiota nameko. The molecular weight of the enzyme was estimated to be 31,000 on gel filtration and 35,000 on SDS-PAGE. The activity was inhibited by Cu2+, Hg2+, molybdate, and tartaric acid. The sequence of N-terminal 20 amino acid residues was analyzed.