To provide a main spindle driving device for multispindle working machine capable of responding to the changes in machining form for a short time at low cost.

This main spindle driving device for multispindle working machine comprises a plurality of crankshafts 10, 15 having crank eccentric shafts 11, 12 and 16, 17, respectively; a plurality of main spindle units 20 each including a main spindle 21, which has at the base end part an eccentric transmission shaft 22 decentered at the same amount as the crank eccentric shafts; a main shaft driving plate body 30 including main spindle driving plate holding frames 31 having bearing holes 32 into which crank eccentric shafts 11, 16 of the crank shafts fit and a main spindle driving plate 34 having bearing holes 35 into which the eccentric transmission shafts of the main spindles fit; and balance weights 40 having bearing holes 41 into which the other crank eccentric shafts 12, 17 of the crank shafts fit.