An engine having a crank mechanism and a balancer mechanism for suppressing vibration produced by the crank mechanism. Acceleration by a primary inertia force of the balancer mechanism and a translation force caused by the inertia force of the balancer mechanism, and acceleration by the primary inertia force of the balancer mechanism and a couple caused by the inertia force of the balancer mechanism are regulated to place the instantaneous rotation center of the engine near a predetermined target position.