A syringe drive device 15 according to the present invention includes: an outer tube fixing portion 31 that detachably fixes an outer tube 22 of a syringe 16; a plunger holder 21 that holds a plunger 17 of the syringe 16; and a drive portion that moves the plunger holder 21 along an axis of the syringe. The outer tube fixing portion 31 includes: a flange catcher 33 facing a rear end of a flange 22a of the outer tube 22, the rear end being located far from the plunger 17 to be pushed; slide portions 34 and 35 that are located in front of a front end of the flange 22a to hold the flange 22a between the flange catcher 33 and the slide portions, the front end being located close to the plunger 17 to be pushed; slide guides 36 and 37 that support the slide portions 34 and 35 so as to be slidable along the axis of the syringe; and a slide portion operation mechanism that is switchable between a first state where the slide portions 34 and 35 slide along the axis of the syringe, and a second state where the slide portions 34 and 35 are held at positions to hold the flange 22a between the flange catcher 33 and the slide portions.