A box cutter includes a housing with a blade slide slidably received therein. A pivotal member is pivotably connected to of the blade slide. An inclined face is defined in one of surfaces of the pivotal member and is gradually raised. The inclined face is connected to a pressing area which has two respective rounded guide portions. A spring is connected between the pivotal member and the housing to maintain the blade slide at the initial position. A button is slidably connected to outside of the cover and a spring is connected between the button and the cover. The button is moved to move the blade slide from the initial position thereof to an extended position. When the blade is cutting a workpiece, the blade is tilt and the pivotal member is pivoted by the cover so that blade slide is retracted into the housing.