Provided are a work point position computing section configured to compute the relative position of a work point set on a bucket with respect to an upper swing structure on the basis of posture information, a target surface setting section configured to set a target surface as a target of excavation work on the basis of design surface information, a primary operation determining section configured to determine which of operations of a boom and an arm is a primary operation as a main operation when the work point is moved along the target surface, and a recommended operation computing section configured to compute a recommended operation amount and a recommended operation direction of a secondary operation as another operation different from the primary operation in the operations of the boom and the arm according to an operation amount and an operation direction of the primary operation.