In a crankshaft of an in-line four-cylinder engine, an arm that is closest to a flywheel has a greater average thickness in a direction of the rotation axis of the crankshaft than those of other arms. Two of the arms that are coupled to both sides of the third journal from the flywheel each have a center of gravity closer to its own counterweight compared to the centers of gravity of the arms that face the two arms with corresponding crankpins in between. Accordingly, the rigidity against torsional deformation and the thickness of oil films on the journals are reliably maintained while suppressing increase in the weight of the entire crankshaft.