A molding system molding a sand mold includes a flask, a tank connected to a compressed air source, including an opened end part, and configured to internally store sand, a nozzle attached to the end part of the tank and configured to guide the sand in the tank into the flask, and a control unit configured to output information about clogging of the nozzle when, during sand filling in which the sand in the tank is introduced into the flask through the nozzle, a relationship where pressure inside the tank is higher than initial pressure during the sand filling in which the sand is introduced into the flask is satisfied.