A supporting structure includes: a step stay which is mounted to a motorcycle frame structure and configured to support a foot step for a passenger; an unit supporting portion provided at the step stay and configured to support an operation unit for manually adjusting a characteristic of a rear wheel shock absorber; a pannier supporting portion provided at the step stay and configured to support a front portion of a pannier mounted to a side portion of a motorcycle body; and a tank supporting portion configured to support a reservoir tank for brake oil. The pannier is disposed rearward of the operation unit, and an operation portion of the operation unit is disposed at a position at which overlap of the operation portion with the step stay and the pannier is avoided as viewed from an outer lateral side.