An aspect of the invention is directed to a lubricating structure of an internal combustion engine for feeding oil from an oil pump to respective portions of the internal combustion engine where a balancer shaft is disposed in parallel with a crankshaft in a crankcase, wherein: a main gallery and an oil passage are provided in the crankcase so that oil can be delivered from the oil pump to the main gallery and the oil of the main gallery can be guided by the oil passage to pass through a bearing of the balancer shaft; and the oil passage feeds the oil that has passed through the bearing of the balancer shaft to a cylinder head.