A rotative member has a first passage and a first surface. A tubular member has a second passage and a concave spherical surface. The second passage is communicable with the first passage according to a rotation angle of the rotative member. The rotative member is rotatable and slidable on the concave spherical surface to form a seal between the rotative member and the tubular member when the concave spherical surface is in pressure contact with the first surface on application of a biasing force. A biasing force application member applies the biasing force to the tubular member. The biasing force application member has a second surface, which is in contact with the tubular member and slidable relative to the tubular member.