A scroll type compressor includes a stationary scroll element, a movable scroll element orbiting about a given axis and cooperating with the stationary scroll element for compressing a fluid in a compression chamber defined between the two scroll elements, and a rotation preventing unit for preventing rotation of the movable scroll element about its own axis. The rotation preventing unit has at least a plurality of pairs of scroll side pins mounted on the movable scroll element and housing side pins mounted on a housing of the compressor. When the compression chamber has a reduced volume of 10 through 22% of an initial volume thereof immediately after completion of sucking of the fluid, at least two of the plurality of scroll side pins are arranged to be symmetrical with one another with respect to a line L.sub.2 which passes through a rotating center O.sub.R of the movable scroll element and is perpendicular to a different line L.sub.1 which passes through the rotating center O.sub.R of the movable scroll element and an orbiting center O.sub.S of the movable scroll element. The two scroll side pins are also arranged on a leading side to the cooperating housing side pins, respectively, in a direction corresponding to a direction of rotation of the movable scroll element about the rotating center O.sub.R.