Water-cooled internal combustion engine

In an internal combustion engine with cylinders and a crankshaft, coolant dis charged from a coolant circulating pump is supplied to a coolant jacket formed in a cylinder block via a coolant jacket formed in a cylinder head. An inlet port through which the coolant discharged from the coolant circulating pump flows into the coolant jacket is provided at one end portion of the cylinder head on an intake side thereof in a cylinder-head center line direction, whereas an outlet port through which the coolant in the coolant jacket is allowed to flow out into a heater core is provided at the other end portion of the cylinder head on an exhaust side thereof.