PURPOSE: To prevent leakage of quantities of odors through the discharge cylinder of a vacuum car by a method wherein a branch pipe is mounted on the suction part of a suction fan to suck odorous gas in a waste storage relay tank and a cap fitted in the discharge cylinder of the vacuum car is attached to the tip part of the branch pipe.

CONSTITUTION: A branch pipe 49 is branched from a suction pipe 4 of a suction fan 3 through a valve 53, a flexible swing arm pipe 50 is attached to the tip of the branch pipe 49, and a hood-form cap 51 completely fitted in a discharge cylinder 48 of a vacuum car 47 is attached to the tip of a swing arm pipe 50. When excrement in a waste storage relay tank is collected by the vacuum car 47, the discharge cylinder 48 is covered with the cap 51. All the odorous gas discharged through the discharge cylinder 48 is sucked through the branch pipe 49 with the aid of the suction fan 3 and deodorized by a deodorizing device. This constitution prevents leakage of odors through the discharge cylinder of the vacuum car.