To provide a lightweight rotor blade pair having high radial load capacity and capable of enduring damage due to foreign matter.

A rotor blade pair 34 includes a platform 40, first and second air foils 36 and 38, and a bottom 42 having first and second walls 52 and 54. The platform 40 has inside and outside radial surfaces 50 and 48. The first and second air foils 36 and 38 extend outside from the outside radial surface 48 of the platform 40. The first and second walls 52 and 54 of the bottom 42 extend outside from the inside radial surface 50 of the platform 40, are connected integrally to each other. A hollow part 56 is formed between these walls and the inside radial surface 50. The first and second walls 52 and 54 are respectively and substantially aligned with the first and second air foils 36 and 38.