[PROBLEMS] To enhance freedom in designing an engine, improve acceleration feeling, provide extremely excellent driving feeling, and enable an engine to be more compact. [MEANS FOR SOLVING PROBLEMS] An in-line four-cylinder engine for a vehicle has a two-plane 90° crankshaft (3). The weight of a crank web for each cylinder is distributed to left and right web half bodies (21a,b-24a,b) to satisfy the expression of (KL−0.25)(0.25−KR)=DR/DL, where KL and KR are balance ratios of web half bodies of each cylinder (where KL≠0.25, KR≠0.25), and DL and DR are the distances from the center in the longitudinal direction of the crankshaft to each crank web half body. This causes the vector locus of first moment of inertia to be substantially a circle to cancel the first moment of inertia by a primary balancer (6).