An object of the present invention is to provide a balancer apparatus for an internal combustion engine that can improve design flexibility in the internal combustion engine. The balancer apparatus includes left and right balancer shafts 21L and 21R each including a balancer weight 21a and a rear-side shaft portion 19b and a front-side shaft portion 19a provided on both sides of the weight portion 21a in a rotational axis direction, a rear-side housing 22R including a bearing holding portion 22Rd surrounding an outer periphery of the rear-side shaft portion 19b and rotatably supporting the rear-side shaft portion 19b, and a front-side housing 22F including a bearing holding portion 22Fd rotatably supporting the front-side shaft portion 19a.