In a scroll compressor, an outer wall curve of a scroll lap of a fixed scroll and an inner wall curve of a scroll lap of an orbiting scroll are formed of involute curves whose basic circle radius is defined as “a”, an inner wall curve of the scroll lap of the fixed scroll and an outer wall curve of the scroll lap of the orbiting scroll are formed of involute curves whose basic circle radius is defined as “b”, and a value of a/b which is a ratio of the basic circle radius a and the basic circle radius b is set to a value exceeding 1.0 and less than 1.5. With this structure, a compression chamber formed on the side of the inner wall of the scroll lap of the orbiting scroll is compressed faster than a compression chamber formed on the side of the outer wall of the scroll lap of the orbiting scroll, and leakage loss during compression process can be reduced.