A support structure for a suspended injector includes a suspended injector having a tubular vertical portion extending in a vertical direction, one or more chamfered portions formed by chamfering an outer peripheral surface near an upper end of the tubular vertical portion, a pair of holding members each having a flat surface formed on an inner peripheral surface of each of the pair of holding members to engage with each of the chamfered portions, each of the pair of holding members holding the tubular vertical portion of the suspended injector by sandwiching the tubular vertical portion of the suspended injector from both sides each of the pair of holding members, and a support structure part configured to fixedly support the pair of holding members, and configured to suspend and support the suspended injector.