A superconducting large thin solenoid magnet was constructed for VENUS detector in TRISTAN 30 GeV e** plus e** minus collider. The magnet has 3. 4 m in warm bore diameter and 5. 24 m in usable length with material thickness of 0. 52 radiation length. The first excitation was successfully performed up to 4000 A with no quench. Several forced quench using a heater mounted on the coil was made to check the safety of operation. The quench propagation velocity was clearly measured in these quenches. The 'quench back' phenomena was observed about one second after the shut off of the power supply. The field quality of the magnet was found to be uniform within the accuracy of 0. 5%.