The Beechcraft 300 Super King Air 350 took off Taichung-Ching Chuan Kang Airport (RMQ) at 10:34 hours for a local aerial photography flight. Due to the 2-ampere circuit breaker which controls power source for the landing gear popped, electricity for the power pack was cut off so the motor could not operate to build up pressure to the hydraulic system. On approach the undercarriage indicator lights showed the gear was not down and locked. A warning sounded as the crew prepared for landing. Instead of executing the manual extension procedure as required, the flight crew decided to land anyway. This resulted in the undercarriage to retract upon touching down on runway 18 at Taichung. There were no personal injuries. The plane sustained damage to the propellers and belly. Findings related to probable causes: 1. The 2-ampere circuit breaker which controls power source for the landing gear popped up after the occurrence aircraft having landed shows that electricity for the power pack was cut off when the aircraft was in the process of landing, so the motor could not operate to build up pressure. 2. When the occurrence aircraft was landing the first time, abnormal status of the indicating light for the landing gear down-and-locked was already existed. It was possible that the 2-ampere circuit breaker which controls the power for power pack of the landing gear had popped up before the first landing attempt, thus incapacitating the hydraulic system, rendering it impossible to build up necessary pressure for operating the landing gear. The subsequent two more operations by the flight crew to lower and down lock the landing gear also failed due to insufficient pressure within the landing gear system. 3. During the occurrence aircraft landing, the landing gear not down and lock indication and warning sound came out when the flight crew extended the landing gear and flaps. The flight crew erroneously judged the not down and lock indication and warning were false alarm. Instead of executing the manual extension procedure as required by the operation manual to lower and down lock the landing gear, the flight crew decided to land anyway. The heavy weight of the aircraft causing all landing gear to retract upon touching ground and causing the aircraft landed on its belly.