PURPOSE:To reduce queer sounds generated at the time of sliding and to eliminate the need for the supply of lubricating oil by constituting a sliding surface part with a 2nd material which is harder than a 1st material constituting a surface part to be slided. CONSTITUTION:Guiding rails 110 and 120 have upper slide tapes 115 and 125 and also lower side tapes 116 and 126 as the 2nd material and formed of a tetrafluoric ethylene resin in which about 70wt.% graphite, etc., is mixed as filling agent. A scanner main body 130 is supported to be freely slide on the slide tapes 115 and 125 with four bushes 135 and a moving mirror pedestal 140 is supported to be freely slide on the slide tapes 116 and 126 with four bushes 145. The bushes 135 and 145 which are the 1st material are formed of the tetrafluoric ethylene resin in which about 40wt.% graphite, etc., is mixed as the filling agent. Thus, stable sliding can be maintained for a long time and failures such as the occurrence of the queer sounds, etc., are not caused.