A mixing apparatus which can reliably prevent an auxiliary liquid from being unintentionally mixed into a main unit even when a failure occurs in a switching device, and which can prevent the switching device or an auxiliary flow route from being damaged even when a pressurizing device malfunctions due to the failure. The mixing apparatus includes a pipe circulating dilution water a pipe circulating a disinfecting solution a pressurizing pump circulating the disinfecting solution in the pipe toward the pipe and a check valve capable of optionally turning on and off the pipe. The mixing apparatus further includes a discharge flow route which consists of a flow route branched from between the check valve and the pressurizing pump in the pipe, and which can discharge the dilution water or the disinfecting solution and an electromagnetic valve which can control the flow route between the check valve and the pressurizing pump in the pipe to have a pressure lower than that of the pipe when not mixing the disinfecting solution with the dilution water.
