Fruiting bodies were degraded themselves by the several glycoside hydrolases after spore releasing from mature fruiting bodies or harvesting. The enzymes involved in autolysis such as glucanase and chitinase have been studied. However, there are almost no information about the relationship between several glycoside hydrolases and autolysis. In this study, we studied to obtain the enzymatic properties of trehalase, and also to get the new information on the relationship between trehalase and autolysis. Crude enzymes were prepared from each fruiting body of Pleurotus sp. (from the immature stage to the autolysis stage) and the trehalase activities were measured at each growth stage. Trehalase activities sharply increased in autolysis stage. Trehalase was partially purified from fruiting bodies of the autolysis stage using various column chromatography and its properties were examined. The optimum temperature was 50 °C and the optimum pH was 4.5. In order to elucidate the localization of trehalase, fruit bodies of the autolysis stage were divided into the stipes and the pileuses, and the each trehalase activity was measured. High trehalase activities were found in the pileuses. Furthermore, in order to elucidate trehalase activities in autolysis more detail, the each fruiting body of autolysis progressing stages was finely divided into the stipes and the pileuses, and their activities were measured. The activities in the outer part of the pileuses were highest at the initial stage of autolysis and the activities shifted from the outer side to the inner side of the pileuses according to the progress of autolysis.