A lubricating device for an internal combustion engine includes an oil tank chamber defined by being separated from a crank chamber by a partition wall that is formed between a crankcase and a crankcase cover of the internal combustion engine. Oil pumped by a scavenge pump is supplied to a tank supply port which is open at an upper portion of the oil tank chamber to the oil tank chamber. The oil stored in the oil tank chamber is sucked from a feed suction port which is open at a lower portion of the oil tank chamber to be supplied to respective regions for lubrication of the internal combustion engine by a feed pump. An oil passage penetrating inside the oil tank chamber is formed below the tank supply port at an upper portion of the oil tank chamber.