To provide balancer shaft structure for an internal combustion engine for preventing the partial contact of a bearing and consequent early wear or the like by making each bearing load almost uniform at a plurality of journal parts of a balancer shaft.

In the internal combustion engine provided with the balancer shaft 20 driven rotatingly by a crankshaft 5, a balance weight provided at the balancer shaft 20 is divided in balance weights 44 and 45, and the balance weights 44 and 45 are arranged in front and in the rear of a journal part 20c. Since the divided balance weights 44 and 45 are arranged in front and in the rear of the journal part 20c in the balancer shaft 20, a couple of force generated to the balance weights 44 and 45 is dispersed to make bearing load almost uniform at the respective journal parts 20a-20d, so that the partial contact of a bearing and consequent early wear or the like can be prevented.