A scroll fluid machine, comprising: a fixed scroll fixed to a housing (3, 103); an orbiting scroll that is configured to engage with the fixed scroll and is configured to be orbitally movable; a rotating shaft that is configured to be supported rotatably with respect to the housing (3, 103) and has an eccentric pin eccentric with respect to a shaft center; and a bush that is interposed between the eccentric pin and the orbiting scroll and is configured to transmit rotational movement of the eccentric pin as orbital movement of the orbiting scroll, wherein an outer shape of the eccentric pin has: a first circular arc formed in a range of an outer shape of the rotating shaft, with a first radius (Ra) having a length exceeding a part of an outer edge of the rotating shaft, the first radius (Ra) having its center at a position of an eccentric center; and a second circular arc (25b, 125b) formed in a portion where the first radius (Ra) exceeds the outer edge, with a second radius (Rb) having a length equal to or less than a radius forming the outer edge, the second radius (Rb) having its center at a position of the shaft center, and a bush side slide surface that faces a pin side slide surface of the eccentric pin is provided in an internal shape of a hole portion of the bush; characterized in that, in the bush, a diameter of the internal shape of the hole portion is formed more largely than that of the outer shape of the eccentric pin in a direction along a radial direction of the eccentric center on the pin side slide surface and thereby, the bush is configured to be able to slidingly move along the pin side slide surface, and the first radius (Ra), the second radius (Rb), the radius, and a distance (ρ) between the position of the shaft center and the position of the eccentric center satisfy a relation of (Ra 2 + ρ 2) 1/2 ≤ Rb ≤ R. a fixed scroll fixed to a housing (3, 103); an orbiting scroll that is configured to engage with the fixed scroll and is configured to be orbitally movable; a rotating shaft that is configured to be supported rotatably with respect to the housing (3, 103) and has an eccentric pin eccentric with respect to a shaft center; and a bush that is interposed between the eccentric pin and the orbiting scroll and is configured to transmit rotational movement of the eccentric pin as orbital movement of the orbiting scroll, wherein an outer shape of the eccentric pin has: a first circular arc formed in a range of an outer shape of the rotating shaft, with a first radius (Ra) having a length exceeding a part of an outer edge of the rotating shaft, the first radius (Ra) having its center at a position of an eccentric center; and a second circular arc (25b, 125b) formed in a portion where the first radius (Ra) exceeds the outer edge, with a second radius (Rb) having a length equal to or less than a radius forming the outer edge, the second radius (Rb) having its center at a position of the shaft center, and a bush side slide surface that faces a pin side slide surface of the eccentric pin is provided in an internal shape of a hole portion of the bush; characterized in that, in the bush, a diameter of the internal shape of the hole portion is formed more largely than that of the outer shape of the eccentric pin in a direction along a radial direction of the eccentric center on the pin side slide surface and thereby, the bush is configured to be able to slidingly move along the pin side slide surface, and the first radius (Ra), the second radius (Rb), the radius, and a distance (ρ) between the position of the shaft center and the position of the eccentric center satisfy a relation of (Ra 2 + ρ 2) 1/2 ≤ Rb ≤ R.