A tank holding device includes a band configured to tighten a hydrogen tank. The band includes a band-shaped base portion extending along an outer circumference of the hydrogen tank, and a plurality of pressing portions projecting from both sides of the base portion in a width direction orthogonal to a longitudinal direction of the base portion and configured to apply a pressing force to an outer peripheral surface of the hydrogen tank by elastically deforming in abutment against the outer peripheral surface of the hydrogen tank. At least an elastic member is provided in a gap between the band and the hydrogen tank to fill the gap.