A temperature adjustment device is capable of suppressing sleeve enlargement and preventing the rattling thereof with a synthetic resin housing. Flanges are formed on the temperature adjustment member. The sleeve has a groove along the circumferential direction on its outer periphery and a lateral hole opening at one end to the groove and penetrating through the wall thickness of the sleeve. A clip member has an outer fitting portion, elastically deformable and fittable to the groove and has an inward convex portion holding the flange from the distal-end side of the sleeve, by being inserted in the lateral hole. The groove wall has a groove-depth wall at the deepest portion opposite to the groove opening and a distal-proximal-end-side curved portion of the groove-depth wall connected to the distal-proximal-end side of the sleeve. The radius of curvature of the distal-end-side curved portion is larger than that of the proximal-end-side curved portion.