A work apparatus comprising: a body; a first robot that is provided on the body so as to be movable in an X direction and a Y direction orthogonal to each other, wherein a first work device is mounted on the first robot; a second robot that is provided on the body at a position different from a position of the first robot in a Z direction orthogonal to the X direction and the Y direction so as to be movable in the X direction and the Y direction, wherein a second work device is mounted on the second robot, wherein the second work device is configured to perform work on an opposite side of a board held by the work apparatus as compared to the first work device; characterized by an inspection mark that is provided on the second robot or the second work device mounted on the second robot; an imaging device that is provided on the first robot and images a side where the second robot is present; first robot-feeding error detecting means configured to detect first robot-feeding errors, which are feeding errors of the first robot rotative to the body in the X direction and the Y direction, on the basis of reference marks on a reference plate disposed on the body that are imaged by the imaging device; relative position detecting means configured to move the first and second robots (20, 50) to inspection positions in the X direction and the Y direction and to detect relative position errors of the first and second robots (20, 50) in the X direction and the Y direction on the basis of the inspection mark that is imaged at the inspection positions by the imaging device; and second robot-feeding error detecting means configured to detect second robot-feeding errors, which are feeding errors of the second robot relative to the body in the X direction and the Y direction, on the basis of the first robot-feeding errors and the relative position errors. a body; a first robot that is provided on the body so as to be movable in an X direction and a Y direction orthogonal to each other, wherein a first work device is mounted on the first robot; a second robot that is provided on the body at a position different from a position of the first robot in a Z direction orthogonal to the X direction and the Y direction so as to be movable in the X direction and the Y direction, wherein a second work device is mounted on the second robot, wherein the second work device is configured to perform work on an opposite side of a board held by the work apparatus as compared to the first work device; characterized by an inspection mark that is provided on the second robot or the second work device mounted on the second robot; an imaging device that is provided on the first robot and images a side where the second robot is present; first robot-feeding error detecting means configured to detect first robot-feeding errors, which are feeding errors of the first robot rotative to the body in the X direction and the Y direction, on the basis of reference marks on a reference plate disposed on the body that are imaged by the imaging device; relative position detecting means configured to move the first and second robots (20, 50) to inspection positions in the X direction and the Y direction and to detect relative position errors of the first and second robots (20, 50) in the X direction and the Y direction on the basis of the inspection mark that is imaged at the inspection positions by the imaging device; and second robot-feeding error detecting means configured to detect second robot-feeding errors, which are feeding errors of the second robot relative to the body in the X direction and the Y direction, on the basis of the first robot-feeding errors and the relative position errors.