An interior permanent magnet motor, comprising: a rotor comprising a permanent magnet; and a stator, wherein the rotor further comprises a rotor core, wherein the rotor core has a magnet insertion hole and a slit, wherein the permanent magnet is inserted into the magnet insertion hole, wherein the magnet insertion hole is curved into an arc shape, and a convex portion side of the arc shape is arranged on a center side of the rotor, wherein the slit is arranged in a region of the rotor core, which is located on a radially outer side of the magnet insertion hole, wherein the magnet insertion hole has a hole outer-side line, a hole inner-side line, and a pair of hole side lines, wherein the hole outer-side line is locatedon the radially outer side of the hole inner-side line, wherein each of the hole side lines connects the hole outer-side line and the hole inner-side line to each other, wherein the hole outer-side line comprises a main arc portion and a pair of concave portions, and wherein an outer-side contour surface of the permanent magnet is formed by a first arc surface having a first arc radius; wherein the hole outer-side line of the magnet insertion hole is formed by the main arc portion having the first arc radius and the pair of concave portions that are located on both sides of the main arc portion; characterized in that: an inner-side contour surface of the permanent magnet is formed by a pair of the second arc surfaces having a second arc radius and a straight surface; wherein the hole inner-side line of the magnet insertion hole is formed by a pair of the second arc surfaces having the second arc radius and a straight surface; wherein the second arc radius is larger than the first arc radius; and wherein the first arc radius and the second arc radius have a common radius center. a rotor comprising a permanent magnet; and a stator, wherein the rotor further comprises a rotor core, wherein the rotor core has a magnet insertion hole and a slit, wherein the permanent magnet is inserted into the magnet insertion hole, wherein the magnet insertion hole is curved into an arc shape, and a convex portion side of the arc shape is arranged on a center side of the rotor, wherein the slit is arranged in a region of the rotor core, which is located on a radially outer side of the magnet insertion hole, wherein the magnet insertion hole has a hole outer-side line, a hole inner-side line, and a pair of hole side lines, wherein the hole outer-side line is locatedon the radially outer side of the hole inner-side line, wherein each of the hole side lines connects the hole outer-side line and the hole inner-side line to each other, wherein the hole outer-side line comprises a main arc portion and a pair of concave portions, and wherein an outer-side contour surface of the permanent magnet is formed by a first arc surface having a first arc radius; wherein the hole outer-side line of the magnet insertion hole is formed by the main arc portion having the first arc radius and the pair of concave portions that are located on both sides of the main arc portion; characterized in that: an inner-side contour surface of the permanent magnet is formed by a pair of the second arc surfaces having a second arc radius and a straight surface; wherein the hole inner-side line of the magnet insertion hole is formed by a pair of the second arc surfaces having the second arc radius and a straight surface; wherein the second arc radius is larger than the first arc radius; and wherein the first arc radius and the second arc radius have a common radius center. an inner-side contour surface of the permanent magnet is formed by a pair of the second arc surfaces having a second arc radius and a straight surface; wherein the hole inner-side line of the magnet insertion hole is formed by a pair of the second arc surfaces having the second arc radius and a straight surface; wherein the second arc radius is larger than the first arc radius; and wherein the first arc radius and the second arc radius have a common radius center.