To provide an cooling system for an internal combustion engine having a cooling fan with appropriate size and output while making the space necessary for the cooling system in the shaft direction minimal.

A cooling system 10 of an engine E has a radiator 14 with two channels comprising a plurality of cores and a motor M actuated by hydraulic pressure and disposed between the cores. The motor M drives a cooling fan 28 that blows air to the radiator 14. Also, oil coolers 30, 32 are disposed between the cores in order to cool oil for actuating the motor M. With this configuration, the space necessary for the radiator 14 in the shaft direction having the fan and fan motor M is made minimal.