A board work system including: a conveying and holding device including a pair of rails configured to support a board, and a changing mechanism configured to change a distance between the pair of rails, the conveying and holding device being configured to convey the board supported by the rails and hold the board at a work position; a work device configured to perform work with respect to the board held by the conveying and holding device from an underside of the board; a moving device configured to move the work device; and a control device, the control device including an acquiring section configured to acquire a rail spacing distance that is the distance between the pair of rails, and an operation control section configured to control operation of the moving device based on the rail spacing distance acquired by the acquiring section.