A molded-case circuit breaker with a main contact position interlock feature, the circuit breaker comprising: a handle that transfers the user's operational force; a switch lever rotatably mounted on a side plate and connected to the handle, with a pressure portion formed on a part of it; a contact part including a movable contact, a fixed contact, and a shaft, wherein the movable contact is mounted on the shaft and rotates with the rotation of the shaft and wherein the shaft has a pair of shaft pins (27a and 27b); an upper link and a lower link connected by a link shaft, wherein the upper link is rotatably mounted on a latch, and the lower link is rotatably mounted on one of the pair of shaft pins (27a and 27b); a shaft link, one end of which is rotatably mounted on the other one of the pair of shaft pins (27a and 27b); a trip lever rotatably mounted on the side plate, one end of which is slidably connected to the shaft link, and the other end of which is connected to a nail of a tripping mechanism, wherein, if the pressure portion makes contact with the contact region, the trip lever rotates the nail, wherein an arc-like slit is formed through the shaft link, and a protrusion is formed at one end of the trip lever to be slidably inserted into the arc-like slit, and wherein the protrusion makes contact at an upper end point of the arc-like slit when in an off state, characterized in that the contact region is on the top of the shaft link; wherein the slit is divided into a first part extending from the upper end point to a point where the protrusion is in the on state and a second part extending from the point where the protrusion is in the on state to a lower end point, wherein when the movable contact and the fixed contact fuse together, the protrusion of the trip lever moves in the second part of the arc-like slit, and the protrusion makes contact with the lower end point. a handle that transfers the user's operational force; a switch lever rotatably mounted on a side plate and connected to the handle, with a pressure portion formed on a part of it; a contact part including a movable contact, a fixed contact, and a shaft, wherein the movable contact is mounted on the shaft and rotates with the rotation of the shaft and wherein the shaft has a pair of shaft pins (27a and 27b); an upper link and a lower link connected by a link shaft, wherein the upper link is rotatably mounted on a latch, and the lower link is rotatably mounted on one of the pair of shaft pins (27a and 27b); a shaft link, one end of which is rotatably mounted on the other one of the pair of shaft pins (27a and 27b); a trip lever rotatably mounted on the side plate, one end of which is slidably connected to the shaft link, and the other end of which is connected to a nail of a tripping mechanism, wherein, if the pressure portion makes contact with the contact region, the trip lever rotates the nail, wherein an arc-like slit is formed through the shaft link, and a protrusion is formed at one end of the trip lever to be slidably inserted into the arc-like slit, and wherein the protrusion makes contact at an upper end point of the arc-like slit when in an off state, characterized in that the contact region is on the top of the shaft link; wherein the slit is divided into a first part extending from the upper end point to a point where the protrusion is in the on state and a second part extending from the point where the protrusion is in the on state to a lower end point, wherein when the movable contact and the fixed contact fuse together, the protrusion of the trip lever moves in the second part of the arc-like slit, and the protrusion makes contact with the lower end point.