A rotary compressor comprising: a first cylinder; a first piston that has a cylindrical shape and revolves along an inner wall surface of the first cylinder and forms a first compression chamber for compressing a fluid between the first piston and the inner wall surface of the first cylinder; and a drive shaft that is rotatable and comprises a first eccentric portion that is eccentric in the first direction with respect to a rotational center axis and to which the first piston is fitted, wherein the drive shaft further comprises: a first shaft portion that is rotatably supported by a first bearing formed on an end plate for closing one end face of the first cylinder and has a cylindrical shape coaxial with the rotational center axis of the drive shaft; and a first coupling portion that couples the first shaft portion with the first eccentric portion, and is configured to satisfy R e1 - e 1 < R 1, wherein R e1 is the radius of the first eccentric portion, R 1 is the radius of the first shaft portion, and e 1 is the eccentricity of the first eccentric portion, the first coupling portion is formed such that its outer surface does not extend out of the outer surface of the first eccentric portion in the radial direction of the drive shaft and is configured to satisfy H C1 < H P1, wherein H C1 is the height of the first coupling portion in the axial direction of the drive shaft, and H P1 is the height of the first piston, and a circumferentially extending groove is formed at an end of the inner peripheral surface of the first piston on the first coupling portion side in the axial direction of the drive shaft in order to avoid contact between the inner peripheral surface of the first piston and the first shaft portion when the first piston is disposed on the outer peripheral side of the first coupling portion and has its inner peripheral surface disposed outside the outer peripheral surface of the first eccentric portion in the radial direction of the drive shaft, characterized in that the first coupling portion penetrates into the end plate in the axial direction. a first cylinder; a first piston that has a cylindrical shape and revolves along an inner wall surface of the first cylinder and forms a first compression chamber for compressing a fluid between the first piston and the inner wall surface of the first cylinder; and a drive shaft that is rotatable and comprises a first eccentric portion that is eccentric in the first direction with respect to a rotational center axis and to which the first piston is fitted, wherein the drive shaft further comprises: a first shaft portion that is rotatably supported by a first bearing formed on an end plate for closing one end face of the first cylinder and has a cylindrical shape coaxial with the rotational center axis of the drive shaft; and a first coupling portion that couples the first shaft portion with the first eccentric portion, and a first shaft portion that is rotatably supported by a first bearing formed on an end plate for closing one end face of the first cylinder and has a cylindrical shape coaxial with the rotational center axis of the drive shaft; and a first coupling portion that couples the first shaft portion with the first eccentric portion, and is configured to satisfy R e1 - e 1 < R 1, wherein R e1 is the radius of the first eccentric portion, R 1 is the radius of the first shaft portion, and e 1 is the eccentricity of the first eccentric portion, the first coupling portion is formed such that its outer surface does not extend out of the outer surface of the first eccentric portion in the radial direction of the drive shaft and is configured to satisfy H C1 < H P1, wherein H C1 is the height of the first coupling portion in the axial direction of the drive shaft, and H P1 is the height of the first piston, and a circumferentially extending groove is formed at an end of the inner peripheral surface of the first piston on the first coupling portion side in the axial direction of the drive shaft in order to avoid contact between the inner peripheral surface of the first piston and the first shaft portion when the first piston is disposed on the outer peripheral side of the first coupling portion and has its inner peripheral surface disposed outside the outer peripheral surface of the first eccentric portion in the radial direction of the drive shaft, characterized in that the first coupling portion penetrates into the end plate in the axial direction.