PURPOSE: To successively move welding members to under plural upper electrodes and spot-weld the multiple parts safely with good workability in a stationary type spot welding machine, by sliding a lower electrode holder on a rail.

CONSTITUTION: When the 1st air cylinder 6 is operated in the direction (a), a lower electrode holder 12 slides on a rail 10 and stops the center of a lower electrode 1 in a predetermined position with a limit switch 52. Thence, upper electrodes 2, 21 for primary welding are lowered and the primary weld zones 8, 81 are spot-welded. Thence, the upper electrodes 2, 21 are moved upward and the 2nd air cylinder 4 is operated in the direction (a) to stop the center of the lower electrode 1 in the next predetermined position and abut the upper electrode 3 for the secondary welding on the secondary weld zone 9, thence spot welding is performed. Upon completion of welding, the 2nd and 1st cylinders 4, 6 are moved successively to slide the lower electrode holder 12 to the direction (b).