PROBLEM TO BE SOLVED: To provide liquid agent for an on-tank type toilet aromatic and washing device capable of stably exhibiting an aromatic effect and washing effect over a long period of time. SOLUTION: This liquid agent L is used in the on-tank type toilet aromatic and washing device in which a liquid agent L in a storage container 11 is guided to a liquid sump part 14, flushing water W is supplied to the liquid sump part 14, and liquid containing the liquid agent L is let flow out to a water storage tank. The viscosity is adjusted so that the quantity of the liquid guided from the storage container 11 to the liquid sump part 14 is a prescribed quantity.
