INTERNAL COMBUSTION ENGINE STRUCTURE

An internal combustion engine structure includes: a crankshaft (10) that converts reciprocating motion of a piston (24) disposed inside a cylinder (12) of an internal combustion engine (2) to be mounted on a vehicle into rotational motion; a case member (11) that houses the crankshaft (10); a balancer shaft (14) that suppresses vibration of the crankshaft (10); a starting device (15) that starts the internal combustion engine (2); and a detection device (16) that is disposed between the balancer shaft (14) and the starting device (15) in a side view and determines the rotation speed of the crankshaft (10).