A profile of a cam (33) of a camshaft (32) is set based on a relationship of a stop position of a vane rotor (36) at a most retarded phase relative to a housing rotor (37). In other words, the profile of the cam (33) arranged in the camshaft (32) is set so that a second opening (110B) of a communication passage (100), which opens in a second retardment chamber (52B), is located upward in a vertical direction from the axis C of the camshaft (32) when the camshaft (32) is at a neutral position, that is, when torque applied from the cam (33) to the camshaft (32) is the smallest.