A cooking appliance, comprising: a main body having a cavity; a door that opens and closes an open front of the cavity; and a latch module that controls an opening and a closing of the door; characterized in that the latch module comprises: a latch that comprises a contact surface, and an extension extended outward from the contact surface and having a sub-contact surface; an elastic body that applies an elastic force to the latch in a first direction (wl); a drive that provides power for the latch to move; and a cam that contacts the contact surface, transmits the power of the drive to the latch and has a first radius, a second radius, and a third radius in a circumferential direction at the outer circumference thereof; wherein the sub-contact surface approaches a surface of the cam or is away from a surface of the cam as the latch moves, wherein the power of the drive is applied through the contact surface so that the latch moves in a second direction opposite to the first direction, and wherein moving of the latch in the second direction is prevented when the sub-contact surface is interfered with the surface of the cam, wherein the first radius has such a radius that the latch is disposed in a first basic position, when the first radius contacts the side of the latch, wherein the second radius has a radius greater than the first radius to further move the latch in the second direction than the first basic position when the second radius contacts the side of the latch so that the latch is disposed in a second basic position, and wherein the third radius has a radius less than the radius of the first radius to allow the latch to further move in the first direction than the first basic position when the third radius contacts the side of the latch so that the latch is disposed in a third basic position in which the latch securely locks the door. a main body having a cavity; a door that opens and closes an open front of the cavity; and a latch module that controls an opening and a closing of the door; characterized in that the latch module comprises: a latch that comprises a contact surface, and an extension extended outward from the contact surface and having a sub-contact surface; an elastic body that applies an elastic force to the latch in a first direction (wl); a drive that provides power for the latch to move; and a cam that contacts the contact surface, transmits the power of the drive to the latch and has a first radius, a second radius, and a third radius in a circumferential direction at the outer circumference thereof; wherein the sub-contact surface approaches a surface of the cam or is away from a surface of the cam as the latch moves, wherein the power of the drive is applied through the contact surface so that the latch moves in a second direction opposite to the first direction, and wherein moving of the latch in the second direction is prevented when the sub-contact surface is interfered with the surface of the cam, wherein the first radius has such a radius that the latch is disposed in a first basic position, when the first radius contacts the side of the latch, wherein the second radius has a radius greater than the first radius to further move the latch in the second direction than the first basic position when the second radius contacts the side of the latch so that the latch is disposed in a second basic position, and wherein the third radius has a radius less than the radius of the first radius to allow the latch to further move in the first direction than the first basic position when the third radius contacts the side of the latch so that the latch is disposed in a third basic position in which the latch securely locks the door. a latch that comprises a contact surface, and an extension extended outward from the contact surface and having a sub-contact surface; an elastic body that applies an elastic force to the latch in a first direction (wl); a drive that provides power for the latch to move; and a cam that contacts the contact surface, transmits the power of the drive to the latch and has a first radius, a second radius, and a third radius in a circumferential direction at the outer circumference thereof; wherein the sub-contact surface approaches a surface of the cam or is away from a surface of the cam as the latch moves, wherein the power of the drive is applied through the contact surface so that the latch moves in a second direction opposite to the first direction, and wherein moving of the latch in the second direction is prevented when the sub-contact surface is interfered with the surface of the cam, wherein the first radius has such a radius that the latch is disposed in a first basic position, when the first radius contacts the side of the latch, wherein the second radius has a radius greater than the first radius to further move the latch in the second direction than the first basic position when the second radius contacts the side of the latch so that the latch is disposed in a second basic position, and wherein the third radius has a radius less than the radius of the first radius to allow the latch to further move in the first direction than the first basic position when the third radius contacts the side of the latch so that the latch is disposed in a third basic position in which the latch securely locks the door.