A board stopping position determination method of a component mounting machine (14, 15, 20) which, in order to transport first and second printed circuit boards (S1, S2) along a conveyance direction and mount electronic components on each, is provided with first and second board conveyance lanes (26, 27) which cause the first and second printed circuit boards (S1, S2) to stop at each set position (P1a to P1c, P2a to P2c) among a plurality of first and second side set positions (P1a to P1c, P2a to P2c) which are set along the conveyance direction, and first and second mounting heads (33a, 33b) which mount the electronic components of first and second component supply devices (29a, 29b), respectively, to the first and second printed circuit boards (S1, S2) which are stopped in each of the set positions (P1a to P1c, P2a to P2c) of the first and second sides, the method being characterized by: a movement time calculation step of calculating respective movement times in which the first and second mounting heads (33a, 33b) move respectively in order to mount the electronic components when the first printed circuit board is positioned in one set position (P1a to P1c) of the first side and the second printed circuit board is positioned in one set position (P2a to P2c) of the second side; an interference loss time calculation step of calculating a waiting time which is a time in which, while one of the first and second mounting heads (33a, 33b) enters an interference area (Aa), the other waits to enter the interference area (Aa) as an interference loss time based on a probability that, when one of the first and second mounting heads (33a, 33b) is anticipated to enter the interference area (Aa), the other is moving within the interference area (Aa), and based on the movement time in the interference area (Aa) in which there is a likelihood that the first and second mounting heads (33a, 33b) which correspond to the respective first and second printed circuit boards (S1, S2) which are each positioned in the same set positions (P1a to P1c, P2a to P2c) as in the movement time calculation step will interfere with each other; and a stopping position determination step of determining the first side set position (P1a to P1c) and the second side set position (P2a to P2c) which are selected from among all combinations as board stopping positions based on total movement times which are calculated for all of the combinations of the first side set position (P1a to P1c) and the second side set position (P2a to P2c) by the movement time calculation step and the interference loss time which is calculated by the interference loss time calculation step. a movement time calculation step of calculating respective movement times in which the first and second mounting heads (33a, 33b) move respectively in order to mount the electronic components when the first printed circuit board is positioned in one set position (P1a to P1c) of the first side and the second printed circuit board is positioned in one set position (P2a to P2c) of the second side; an interference loss time calculation step of calculating a waiting time which is a time in which, while one of the first and second mounting heads (33a, 33b) enters an interference area (Aa), the other waits to enter the interference area (Aa) as an interference loss time based on a probability that, when one of the first and second mounting heads (33a, 33b) is anticipated to enter the interference area (Aa), the other is moving within the interference area (Aa), and based on the movement time in the interference area (Aa) in which there is a likelihood that the first and second mounting heads (33a, 33b) which correspond to the respective first and second printed circuit boards (S1, S2) which are each positioned in the same set positions (P1a to P1c, P2a to P2c) as in the movement time calculation step will interfere with each other; and a stopping position determination step of determining the first side set position (P1a to P1c) and the second side set position (P2a to P2c) which are selected from among all combinations as board stopping positions based on total movement times which are calculated for all of the combinations of the first side set position (P1a to P1c) and the second side set position (P2a to P2c) by the movement time calculation step and the interference loss time which is calculated by the interference loss time calculation step.