The invention provides an improved bridge maintenance device including a mixing box. The improved bridge maintenance device is characterized in that a mounting groove is formed in the inner wall bodyof the mixing box; an inner shell body is arranged in the mounting groove in a sliding fit mode; a mixing cavity is formed upward in the opening of the mounting groove of the inner shell body; a firstrotating cavity, a second rotating cavity and a third rotating cavity are correspondingly formed in the inner wall body of the mixing box which is located at the bottom end of the mounting groove; arotating shaft, extending transversely, is arranged in the second rotating cavity in a rotating fit mode; the rotating shaft is connected with the mixing box in a rotating fit mode, and the tail endsof the left and right sides of the rotating shaft correspondingly extend into the inner wall of the left side of the first rotating cavity and the inner wall of the right side of the third rotating cavity; and a driving motor is fixedly arranged in the mixing box which is between the first rotating cavity and the second rotating cavity. The efficiency of mixing mud is greatly enhanced.