A drainage device with a low-noise drainage shell for air-conditioning equipment is disclosed to include a housing, a motor, a radiating fan, a drainage shell, and a drainage blade. The motor is mounted in the housing. The radiating fan is mounted in the housing above the motor. The drainage shell mounted in the housing and has a drainage partition block extended from an inside wall thereof to divide the inside space of the drainage shell into an accommodation trough and a drainage trough in communication with each other. The drainage partition block has a backwardly downwardly tilted sloping surface. Thus, the sloping surfaces of the drainage partition block can guide the drain water smoothly to the drainpipe to reduce the water resistance, thereby significantly reducing the level of water drain noise.