The present invention relates to a technology that can simultaneously control the flow rate of a coolant and perform variable separate cooling by controlling the opening rate of a flow control valve. The flow control valve has an inlet port connected to a coolant outlet of a cylinder block and a plurality of outlet ports connected to a cooling inlet port of an engine such that the opening rate of a first outlet port is symmetrically changed in a first direction and a second direction from a mid-operation angle of the entire operation section of the flow control valve.