The invention provides a hollow fiber spinning nozzle or spinning plate washing device and an application method. The hollow fiber spinning nozzle or spinning plate washing device comprises an ultrasonic washing device, washing equipment and a solvent circulating pump, wherein a discharging hole is formed in the bottom of the ultrasonic washing device; the discharging hole is connected with a valve, the solvent circulating pump, a valve, a filter and the washing equipment in sequence through a fifth branch pipe; the washing equipment is vertically arranged above the ultrasonic washing device; and the fifth branch pipe is provided with an automatic controller. Preferably, the hollow fiber spinning nozzle or spinning plate washing device further comprises a pressure gauge, wherein the pressure gauge is located on the fifth branch pipe and is located between the filter and the washing equipment. The invention provides the device for simultaneously washing a film casting solution channel and a core solution channel of a spinning nozzle or a spinning plate and the application method; and the problems that a core solution pipe is damaged, is not concentric after being mounted and the like, caused by detaching and washing, are reduced, and the washing efficiency is improved.