Impulsive sound of an Oldham ring is reduced and a driving noise of a scroll compressor is prevented from increasing. When a width of the key of the Oldham ring made of iron-based material is defined as t and a width of the orbiting-side key groove in the back surface of the surface plate of the orbiting scroll made of aluminum-based material and a width of the fixed-side key groove of the main bearing member made of aluminum-based material on the side of a thrust surface are defines as s, a gap d generated at s−t with respect to a key pitch L of the Oldham ring I set in a range of (6×10−5)≦d/L≦(3.5×10−4). With this, even if the key of the Oldham ring vibrates in the key groove, a collision force against the key groove is weakened, impulsive sound of the Oldham ring becomes small, and a driving noise of the scroll compressor is can be reduced.