Internal combustion engine with regenerator

An internal combustion engine (1) includes a circulation system (C) which circulates a heat medium, a cylinder head part channel (23a) which circulates the heat medium into a cylinder head (1a), a cylinder block part channel (23b) which circulates the heat medium into a cylinder block (1b), a connecting channel (23c) which connects the cylinder head part channel (23a) with the cylinder block part channel (23b), heat supply means (23) that supply heat accumulated in the regenerator (10) to the internal combustion engine (1), and restraining means (38) that restrain heat circulation in the connecting channel (23c) when heat is supplied by the heat supply means (23) or the internal combustion engine (1) is under cold conditions.