1. A support pin arrangement determination assisting method comprising:displaying an image including an image of a board, said image of the board including a shape data of an arrangement of an already mounted component on an already mounted surface of the board;
inputting an arrangement position of the support pin provided on a support plate in a board holding unit to the displayed image;
superimposing the arrangement position of the support pin on the image of the board to create a composite image; and
displaying the composite image which provides the support pin arrangement determination assistance,
wherein the arrangement position of the support pin includes an image of a top portion of the support pin and an image of a contact portion of the support pin which is located on a tip side of the top portion, the contact portion has a sectional shape smaller than that of the top portion, and the contact portion contacts and supports a lower surface of the board.