A rotary valve comprising: a rotor which is rotated to open and close a flow passage; and a casing which accommodates the rotor, wherein the casing is provided with a rotor accommodating space which rotatably accommodates the rotor and includes at least one inflow side opening through which a fluid flows in from the outside to the rotor accommodating space and at least one outflow side opening (25a, 26a) through which the fluid flows out from the rotor accommodating space to the outside, respectively at a position opposite to an outer circumferential surface of the rotor, the rotor is formed in a cylindrical shape having an internal space, the outer circumferential surface of the rotor is provided with a rotor outer circumferential opening which communicates with one opening of the inflow side opening and the outflow side opening (25a, 26a) of the casing when being opposite to the one opening and a rotor outer circumferential blocking surface which blocks the one opening when being opposite to the one opening, a first interval is formed between the outer circumferential surface of the rotor and an inner circumferential surface of the casing which opposes the outer circumferential surface, excluding the one opening which is blocked by the rotor outer circumferential blocking surface of the rotor, such that the fluid can flow through the first interval, characterized in that right and left end surfaces of the rotor are provided with end surface side openings which communicate with the internal space, and a second interval is formed between the right end surface of the rotor and the casing and between the left end surface of the rotor and the casing such that the fluid can flow in from the end surface opening to the rotor or can flow out from the rotor. a rotor which is rotated to open and close a flow passage; and a casing which accommodates the rotor, wherein the casing is provided with a rotor accommodating space which rotatably accommodates the rotor and includes at least one inflow side opening through which a fluid flows in from the outside to the rotor accommodating space and at least one outflow side opening (25a, 26a) through which the fluid flows out from the rotor accommodating space to the outside, respectively at a position opposite to an outer circumferential surface of the rotor, the rotor is formed in a cylindrical shape having an internal space, the outer circumferential surface of the rotor is provided with a rotor outer circumferential opening which communicates with one opening of the inflow side opening and the outflow side opening (25a, 26a) of the casing when being opposite to the one opening and a rotor outer circumferential blocking surface which blocks the one opening when being opposite to the one opening, a first interval is formed between the outer circumferential surface of the rotor and an inner circumferential surface of the casing which opposes the outer circumferential surface, excluding the one opening which is blocked by the rotor outer circumferential blocking surface of the rotor, such that the fluid can flow through the first interval, characterized in that right and left end surfaces of the rotor are provided with end surface side openings which communicate with the internal space, and a second interval is formed between the right end surface of the rotor and the casing and between the left end surface of the rotor and the casing such that the fluid can flow in from the end surface opening to the rotor or can flow out from the rotor.