We investigated hypoglycemic effect of ethanol (EtOH) and ethyl acetate extract acetate (AcOEt) extracts in streptozotocin- (STZ-) induced diabetic mice. Our data showed the maximum inhibitory effect on the fasting plasma glucose (FPG) level was detected in STZ-induced diabetic mice administered with 400 mg/kg AcOEt extract of P. baumii. A lower glycated albumin (GA) level and a higher insulin level were observed in 400 mg/kg AcOEt and EtOH extract groups. Moreover, 400 mg/kg AcOEt and EtOH extract exhibited a stronger effect on increasing size and cell number of islets. The insulin expression level of β-cells and integrated optical density (IOD) value were significantly increased by the administration of 400 mg/kg AcOEt and EtOH extracts. Taken together, AcOEt and EtOH extracts of P. baumii fruiting body exhibited considerable hypoglycemic effect on STZ-induced diabetic mice.