A slider is displaceable in an axial direction on guide sections of a cylinder tube through a guide mechanism. A first elastic member is interposed between a first bearing support member of the guide mechanism and one retaining section of the slider. A bearing installed in the first bearing support member, is pressed continuously toward the guide section. A second bearing support member is installed via a second elastic member between the guide section and another retaining section of the slider. A bearing provided on the second bearing support member is pressed toward the guide section by means of a resilient force of the second elastic member.