A hermetic compressor, comprising: a cylinder having its inner circumferential surface which forms a compression chamber in an elliptical shape; a roller configured to eccentrically rotate within the cylinder, and a vane (351,352,353) coupled with the roller to divide the compression chamber into a plurality of spaces (333a, 333b, 333c), the vane being configured to, as the roller rotates, conform to the distance between the roller and the inner circumferential surface of the cylinder, whereby, as the roller rotates, a respective volume of the plurality of spaces (333a, 333b, 333c) of the compression chamber is changed, wherein, with respect to a first center line passing through a center (Oc) of the cylinder and a contact point where the inner circumferential surface of the cylinder and an outer circumferential surface of the roller are closest to each other, a first half of the inner circumferential surface positioned at one side of the first center line has a center point (O') that is the center of the first half at which the two partial ellipses (332a',332a") forming the first half and having the same sum of distances to two focal points for every point thereon meet each other, and a second half of the inner circumferential surface positioned at the other side of the first center line has a second center point (O") that is the center of the second half at which two partial ellipses (332b'.332b") forming the second half and having the same sum of distances to two focal points for every point thereon meet each other, wherein the first center point (O') and the second center point (O") are spaced apart from the center (Oc) of the cylinder, wherein the first center point (O') and the second center point (O") are positioned on the first center line, at different separation distances from the center of the cylinder (Oc). a cylinder having its inner circumferential surface which forms a compression chamber in an elliptical shape; a roller configured to eccentrically rotate within the cylinder, and a vane (351,352,353) coupled with the roller to divide the compression chamber into a plurality of spaces (333a, 333b, 333c), the vane being configured to, as the roller rotates, conform to the distance between the roller and the inner circumferential surface of the cylinder, whereby, as the roller rotates, a respective volume of the plurality of spaces (333a, 333b, 333c) of the compression chamber is changed, wherein, with respect to a first center line passing through a center (Oc) of the cylinder and a contact point where the inner circumferential surface of the cylinder and an outer circumferential surface of the roller are closest to each other, a first half of the inner circumferential surface positioned at one side of the first center line has a center point (O') that is the center of the first half at which the two partial ellipses (332a',332a") forming the first half and having the same sum of distances to two focal points for every point thereon meet each other, and a second half of the inner circumferential surface positioned at the other side of the first center line has a second center point (O") that is the center of the second half at which two partial ellipses (332b'.332b") forming the second half and having the same sum of distances to two focal points for every point thereon meet each other, wherein the first center point (O') and the second center point (O") are spaced apart from the center (Oc) of the cylinder, wherein the first center point (O') and the second center point (O") are positioned on the first center line, at different separation distances from the center of the cylinder (Oc).