An internal combustion engine includes a crankcase that rotatably supports a crankshaft, a case cover that liquid-tightly covers a side of the crankcase, a cylinder block that is joined to the crankcase and divides a plurality of cylinders in a V-type arrangement in which the cylinders are disposed above a virtual horizontal plane including a rotational axis of the crankshaft and intersect each other at a bank angle, a to-be-detected body that rotates integrally with the crankshaft, and a detection sensor that is mounted from the outside on the crankcase at a position higher than the virtual horizontal plane and is made to face a trajectory of the to-be-detected body to generate a pulse signal in response to movement of the to-be-detected body. This provides, in a so-called V-type internal combustion engine, a structure for disposing a detection sensor that can detect the angular velocity of a crankshaft with high precision.