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, 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, and a deformation limiting portion configured to limit deformation of the pressing portions to a specified amount.