A nonconforming product removing unit is disposed between a folding unit and a counter ejector of a box making machine, and includes a sort-out unit that conveys a corrugated board box whose joint is judged to be good by a judging unit to the counter ejector, and on the other hand discharges a corrugated board box whose joint is judged to be bad by the judging unit. Accordingly, only the conforming corrugated board box can be conveyed to the counter ejector. Therefore, the nonconforming board box can be removed easily, without requiring complicated work of taking out the nonconforming corrugated board box from among corrugated board boxes sorted into a predetermined number of batches by the counter ejector, and re-sorting only the conforming corrugated board boxes into a predetermined number of batches.