There is provided a potential measuring device of non-contact type which can improve measurement sensitivity. A potential measuring device which measures a charged object in a non-contact manner with a sensor includes: a first shutter and a second shutter each having a shutter part provided with an opening and a leaf spring part; a magnet attached to the leaf spring part of each of the first shutter and the second shutter; a yoke on which a coil is disposed, the coil applying an alternating magnetic field to the magnet of each of the first shutter and the second shutter to cause the shutter part to reciprocate via the leaf spring part; and a natural frequency adjusting means for adjusting a natural frequency of at least one of a first shutter system including the first shutter and the magnet and a second shutter system including the second shutter and the magnet.