A chain guide device wherein it is unnecessary to make a chain guide body a thick and heavy member to enhance the productivity of the chain guide body. The chain guide body is split into a left guide half having a left-side upper split surface and a left-side lower split surface which are formed along a longitudinal direction of a chain and a right guide half having a right-side upper split surface and a right-side lower split surface. The guide bodies, which are roughly U-shaped, can be easily demolded after injection molding to enhance productivity. The contact of the chain with the split surfaces is lessened, as compared with the case where split surfaces are inclined at an angle relative to the longitudinal direction of the chain. Accordingly, wearing of the split surfaces is restrained, and it is unnecessary to make the chain guide body greater in thickness and weight.