To provide a parts order support method for providing support to facilitate parts orders for each supplier.

The parts order support method includes an input date acquisition step (S300) for acquiring the date of input; a first reading step (S304) for reading lead time for a predetermined supplier and a predetermined delivery rank from a rank master storage part 104; a second reading step (S306) for reading a delivery calendar 203 for the predetermined supplier and the predetermined delivery rank from a calendar storage part 105; a determining step (S308) for determining whether or not a date ahead of the date of input by the lead time coincides with a deliverable date indicated by the delivery calendar 203; and an order date reporting step (S318) for reporting the date of input as an order date for the predetermined supplier and the predetermined delivery rank if the date is determined to coincide with the deliverable date in the determining step.