A refrigerant circulation system, comprising: a first refrigerant circuit (14, 16, 16a, 16b) for returning a refrigerant that passes through a main body of an internal combustion engine to the main body after causing the refrigerant to perform heat exchange with a first heat exchanger (20, 22); a control valve that is provided in the first refrigerant circuit (14, 16, 16a, 16b), and includes a rotor that is rotatable around a rotation axis; a second refrigerant circuit (14, 16c) that is connected to the control valve, and is for returning the refrigerant which passes through the main body to the main body after causing the refrigerant to perform heat exchange with a heater for in-vehicle air-conditioning; and control means for controlling a rotational operation of the rotor, based on an operation plan that is set by relating opening and closing states of branch channels (16a, 16b) of the first refrigerant circuit (14, 16, 16a, 16b) and a branch channel of the second refrigerant circuit (14, 16c) with a rotation angle of the rotor from a reference position, wherein the operation plan comprises an all passing mode that changes the opening and closing states when there is a request to pass the refrigerant through the heater for in-vehicle air-conditioning, from a state in which all the branch channels (16a, 16b, 16c) are closed to a state in which all the branch channels (16a, 16b, 16c) are opened, and a partial cutoff mode that changes the opening and closing states of the branch channels (16a, 16b, 16c) when there is no request to pass the refrigerant through the heater for in-vehicle air-conditioning, from the state in which all the branch channels (16a, 16b, 16c)are closed to a state in which only the branch channels (16a, 16b) of the first refrigerant circuit (14, 16, 16a, 16b) are opened, wherein a rotation angle area corresponding to the all passing mode and a rotation angle area corresponding to the partial cutoff mode are separated from each other by a rotation angle area (d) in which all the branch channels (16a, 16b, 16c)are closed, characterized in that the control means is configured to prohibit rotation of the rotor to the rotation angle area (d) in which all the branch channels (16a, 16b, 16c) are closed, following a mode switch request between the all passing mode and the partial cutoff mode when a temperature of the refrigerant which passes through the main body is higher than an upper limit temperature of the refrigerant which is determined based on an operating state of the internal combustion engine. a first refrigerant circuit (14, 16, 16a, 16b) for returning a refrigerant that passes through a main body of an internal combustion engine to the main body after causing the refrigerant to perform heat exchange with a first heat exchanger (20, 22); a control valve that is provided in the first refrigerant circuit (14, 16, 16a, 16b), and includes a rotor that is rotatable around a rotation axis; a second refrigerant circuit (14, 16c) that is connected to the control valve, and is for returning the refrigerant which passes through the main body to the main body after causing the refrigerant to perform heat exchange with a heater for in-vehicle air-conditioning; and control means for controlling a rotational operation of the rotor, based on an operation plan that is set by relating opening and closing states of branch channels (16a, 16b) of the first refrigerant circuit (14, 16, 16a, 16b) and a branch channel of the second refrigerant circuit (14, 16c) with a rotation angle of the rotor from a reference position, wherein the operation plan comprises an all passing mode that changes the opening and closing states when there is a request to pass the refrigerant through the heater for in-vehicle air-conditioning, from a state in which all the branch channels (16a, 16b, 16c) are closed to a state in which all the branch channels (16a, 16b, 16c) are opened, and a partial cutoff mode that changes the opening and closing states of the branch channels (16a, 16b, 16c) when there is no request to pass the refrigerant through the heater for in-vehicle air-conditioning, from the state in which all the branch channels (16a, 16b, 16c)are closed to a state in which only the branch channels (16a, 16b) of the first refrigerant circuit (14, 16, 16a, 16b) are opened, wherein a rotation angle area corresponding to the all passing mode and a rotation angle area corresponding to the partial cutoff mode are separated from each other by a rotation angle area (d) in which all the branch channels (16a, 16b, 16c)are closed, characterized in that the control means is configured to prohibit rotation of the rotor to the rotation angle area (d) in which all the branch channels (16a, 16b, 16c) are closed, following a mode switch request between the all passing mode and the partial cutoff mode when a temperature of the refrigerant which passes through the main body is higher than an upper limit temperature of the refrigerant which is determined based on an operating state of the internal combustion engine.