A sheet detection device for detecting a sheet which passes through a sheet transport path (203,404,405), comprising: a moving member including an interference part; a support member which slidably supports the moving member in a manner that allows a change in a posture thereof between a protruding posture in which the interference part protrudes to the sheet transport path and a retreating posture in which the interference part retreats from the sheet transport path relative to the protruding posture, and which includes a rotating axis (721,722) extending in a direction that is orthogonal to the sliding direction, and rotates about the rotating axis to thereby cause the moving member to rotate about the rotating axis; a first bias member which biases the moving member so that the moving member takes the protruding posture; and a detection unit which performs a detection operation of the sheet based on the rotation of the moving member, characterized in that the moving member including the interference part is capable of interfering with the sheet that passes through the sheet transport path such that the moving member turns in a first direction along a forward direction in a state of maintaining the protruding posture when the sheet passes through the sheet transport path in the forward direction and the sheet interferes with the interference part of the moving member in the protruding posture, and the moving member turns in a second direction that is opposite to the first direction, and changes the posture from the protruding posture to the retreating posture against a biasing force of the first bias member when the sheet once stopped on the sheet transport path is pulled out in a reverse direction and the sheet interferes with the interference part of the moving member in the protruding posture. a moving member including an interference part; a support member which slidably supports the moving member in a manner that allows a change in a posture thereof between a protruding posture in which the interference part protrudes to the sheet transport path and a retreating posture in which the interference part retreats from the sheet transport path relative to the protruding posture, and which includes a rotating axis (721,722) extending in a direction that is orthogonal to the sliding direction, and rotates about the rotating axis to thereby cause the moving member to rotate about the rotating axis; a first bias member which biases the moving member so that the moving member takes the protruding posture; and a detection unit which performs a detection operation of the sheet based on the rotation of the moving member, characterized in that the moving member including the interference part is capable of interfering with the sheet that passes through the sheet transport path such that the moving member turns in a first direction along a forward direction in a state of maintaining the protruding posture when the sheet passes through the sheet transport path in the forward direction and the sheet interferes with the interference part of the moving member in the protruding posture, and the moving member turns in a second direction that is opposite to the first direction, and changes the posture from the protruding posture to the retreating posture against a biasing force of the first bias member when the sheet once stopped on the sheet transport path is pulled out in a reverse direction and the sheet interferes with the interference part of the moving member in the protruding posture.