A crankshaft holding structure 10 for use in an internal combustion engine has a front crankshaft 35 supported by a radial roller bearing 25 that is fixed to a crankcase 11 and has an inner side surface 26a. A land 40 of the front crankshaft 35 is held in abutment against the inner side surface 26a to limit crankshafts 30, 35 against axial elongation and deformation. The radial roller bearing 25 has an outside diameter D1 that is the same as an outside diameter of a radial ball bearing 20. The forgoing arrangement includes simplified bushings cast in a crankcase and having bearing press-fitted therein, that allows the bushings to be used as common parts.