PURPOSE: To obtain a cleaning device capable of constantly keeping the number of particles bonded onto a semiconductor wafer carrier at less than a specific value by a method wherein the cleaning device is provided with a device to measure the particles contained in the pure water in a carrier cleaning vessel.

CONSTITUTION: The title cleaning device is provided with a device 9 to measure the particles contained in pure water 4 in a carrier cleaning vessel 1. For example, a carrier 3 is put in a carrier receiver 2 in the carrier vessel 1 by a carrying arm; jet cleaning is started using a jet nozzle 5; and simultaneously with the cleaning start, the stagnated pure water after the jet cleaning process is injected into the laser particle counter 9 through a piping 6 using a drainage pump 10 so as to count the particles contained in the pure water 4. Next, when the number of particles is less than a specific level e.g. ten a comparator detects the numbers to finish the cleaning process for drying up the carrier 3. In such a constitution, the pure water 4 shall be constantly drained through drainage pipes 7, 8.