To achieve extremely favorable operating feeling and compactization.

The parallel multi-cylinder four-cycle engine is equipped with a valve gear G provided to a cylinder to intake and discharge air, a crank shaft 24 having a crank pin for supporting a connecting rod provided to each cylinder and a crankweb for supporting the crank pin, and a balancer shaft 32 arranged parallel to the crank shaft 24 and provided with a balance weight to eliminate couple of forces generated by primary inertia. A valve drive transmission mechanism H for transmitting power from the balancer shaft 32 to the drive gear G is provided to the engine.