To prevent urine from flowing back from the inside of a urinal even when the angle of the urinal is shifted during urination and to prevent the degradation of an appearance even at the time of being arranged on a bedside by performing installation to the opening part of the urinal.

In this urinal auxiliary tool freely attachably and detachably installed to the upper opening part of the urinal, a cylindrical body 2 in a tapered shape composed of an elastic member, an auxiliary tool main body 1 constituted of a frame body 4 installed to the upper opening part 3 of the cylindrical body 2 and a holding body 5 provided with plural holes mounted to the other end of the cylindrical body and a valve mechanism for preventing the urine from flowing back inside the auxiliary tool main body 1 are installed.