To provide a bearing structure of an engine, which can prevent displacement of a rotation shaft rotatably and pivotally supported inside an engine case and can be easily assembled.

An engine 11 is equipped with: an engine case 12; bearing holders 79, 83 attached to the engine case 12; bearing members (ball bearing 80 and needle bearing 71) supported by the bearing holders 79, 83; and a transmission 72 including a transmission shaft (transmission output shaft 33) rotatably and pivotally supported by the bearing members (ball bearing 80 and needle bearing 71). In the engine 11, an expansion member 80 having a coefficient of thermal expansion higher than that of the engine cases 12 and the bearing holders 79, 83 is disposed between the engine case 12 and the bearing holders 79, 83.