An engine balancer includes a pair of balancer shafts and a balancer housing for housing the balancer shafts, and is placed in an oil pan at the bottom of an engine. The balancer housing includes a pair of front and rear bearing walls respectively supporting the balancer shafts with rolling bearings interposed therebetween. The bearing walls of the balancer housing are attached to bearing walls for a crankshaft. The housing body has an aperture at the top thereof. The aperture of the housing body is covered with a plate-shaped cover member thinner than a member forming the housing body.