Abstract: A window for an acid-base tank suitable for arrangement on a cleaning machine including at least one acid-base tank with an opening on a sidewall of the acid-base tank is described. The window for the acid-base tank at least includes a supporting plate, an annular washer, a transparent observe window and a transparent separation plate. The supporting plate has the same shape as the opening on the sidewall of the cleaning machine, is disposed on the opening, and has a first window opening. The annular washer is disposed on the supporting plate around the first window opening. The transparent observe window is pressed and covered on the annular washer. The transparent separation plate located between the supporting plate and the acid-base tank is disposed on the supporting plate and covers the first window opening. Furthermore, the chemical resistance of the transparent separation plate is better than that of quartz.