A cleaning device of the present invention simultaneously cleans two different hydraulic oil tubes of an aircraft. The cleaning device has a supply flow path, a return flow path, a valved connection tube, a connection tube on-off valve and a control section. The supply flow path is connected to a supply end of a first hydraulic oil tube. The return flow path is connected to a supply end of a second hydraulic oil tube. The valved connection tube is arranged between a connection end of the first hydraulic oil tube and a connection end of the second hydraulic oil tube and fluidly connects the first and second hydraulic oil tubes. The connection tube on-off valve is arranged in a flow path of the valved connection tube and controls a flow rate of a cleaning agent flowing through the valved connection tube according to an instruction from the control section.