The present invention relates to a medium thickness detection apparatus. The present invention has the first roller 120 is fixedly installed in the feed channel (110) of the medium (m), the first roller 120 as in the contact medium (m) of the first roller (120 when passing ) falls while moving upward by the thickness of the medium (m) and, and when the medium (m) is completely passed through the second roller 130 installed to move downward again. The second roller 130 has one end connected to the second roller 130. The other end of the moving direction and a length of the link 150 is connected, the link 150 to move in the same direction, a portion overlapping the state resistance of the strain gage sensor 160 for measuring the amount of deformation that occurs in accordance with the movement of the link 150 in the resistance value are installed on. So, medium (m) is moved when the strain gauge 160 by the thickness of the medium (m) is the deformation occurs, the deformation amount is output in the resistance value. Using such a resistance value can be accurately detect the thickness of the medium. In addition the amount of deformation of the strain gauges than the moving distance of the moving roller moved by the thickness of the medium (m) using the lever principle of the link to more common when installed between the moving rollers and the strain gage, further the thickness of the medium It can be precisely detected.