PURPOSE: An endoscope washer disinfector and a preparation method of disinfection liquid for the same are provided, which can reduce bad smell of the peracetic acid in exchange of the antiseptic solution. CONSTITUTION: An endoscope washer disinfector comprises a concentrate feeding unit(110) which supplies the concentrate(132) in the bottle to the antiseptic solution tank a bottle cleaning unit(112) which supplies the bottle washing solution(136) to the bottle and washes the bottle a first detection unit which detects that the concentrate of the predetermined amount is supplied to the antiseptic solution tank(87) a second detection unit which detects concentration of antiseptic solution and a control unit which stops the bottle cleaning unit.
