Diode-type nanotweezers including a first arm and a second arm that project from a holder and are opened and closed by an electrostatic force so as to hold a nanosubstance. The first arm is formed by a gate nanotube fastened at its base end to the holder, and its tip end protrudes from the holder. The second arm is formed by a nanotube diode fastened at its two base ends to the holder and have a diode characteristic portion at its tip end. Diode current and diode voltage applied between the base ends of the arms shows a non-linear diode characteristic such as varistor and rectification. When a gate voltage is applied between the gate nanotube and the nanotube diode, the arms are controlled and a grip strength for a nanosubstance held by the arms is detected by changes in the gate voltage or the diode current.