1. A group determination method, the method comprising:a step of grouping a plurality of types of mounting boards that are production targets into a sequential combination of a plurality of groups of mounting boards, each group being common in an arrangement of a plurality of component suppliers, in a component mounting line including a plurality of component mounters, each component mounter including a component supply carriage capable of attaching and detaching the plurality of the component suppliers for supplying components,
a step of calculating an external set-up work time for an external set-up work by which component suppliers to be used in a group that is a next production target of a group under production in the component mounting line are arranged in a component supply carriage when the component supply carriage is removed from the component mounting line; and
a step of calculating a production completion time at which production of all the mounting boards that are the production targets is completed in consideration of the external set-up work time,
a step of determining a sequential combination of a plurality of groups of mounting boards that causes a production completion time to be shortened from the calculated production completion time by re-grouping the plurality of types of mounting boards.