An internal combustion engine includes: a cylinder block having a block cooling water passage that supplies cooling water to a plurality of cylinder bores, and an inter-bore cooling water passage provided between cylinder bores that supplies cooling water between the cylinder bores; a cylinder head having a first cooling water passage to which cooling water is supplied from the block cooling water passage, and a second cooling water passage, which is provided independently from the first cooling water passage, and to which cooling water is supplied from the inter-bore cooling water passage; a heat exchanger; a first cooling water introducing part that leads cooling water, which is flown out from the first cooling water passage, to the heat exchanger; and a second cooling water introducing part that leads cooling water, which is flown out from the second cooling water passage, to a downstream side of the heat exchanger.