The invention discloses a mechanical device for pesticide application. The mechanical device comprises a pesticide application machine body; a stirring box is fixedly arranged at the top of the rightside of the pesticide application machine body; a stirring chamber is arranged in the stirring box; a first cavity is arranged in the pesticide application machine body right under the stirring cavity; a first rotating shaft extending upward and downward is in rotatably and cooperatively connected between the first cavity and the stirring cavity; the top extending end of the first rotating shaft extends into the stirring cavity and is dynamically connected with a stirring mechanism; the bottom extending end of the first rotating shaft extends into the first cavity and is fixedly provided witha first cone pulley; a second cavity extending upward is arranged in the pesticide application machine body at the left side of the first cavity; a third cavity extending forward and backward is arranged in the pesticide application machine body at the right side of the first cavity; the front and rear extending ends of the third cavity respectively penetrate through the front and rear end faces of the pesticide application machine body; and a sliding guide rail extending forward and backward is slidably and cooperatively connected in the third cavity.