To enable a load to an occupant's lower limbs from an airbag to be small while widely securing a protective area by an airbag to the upper portion of the knee.

The occupant's lower limb protective device for a vehicle protects the occupant's lower limb A by expanding development of the airbag 11 disposed in front of the occupant's lower limb A toward the occupant's lower limb A with the gas supplied from an inflator 12 at the time of collision of a vehicle. The device is provided with a lower expansion part 11a which expandingly develops with the gas supplied from the inflator 12 and protects the occupant's knee front portion A1 and the shin A2, and an upper expansion part 11b which expandingly develops with the gas supplied from the lower expansion part11a and protects the occupant's knee upper portion A3 on the airbag 11. It is provided with straps 11c, 11d which allow the gas pressure in the upper expansion part 11b to lower than the gas pressure in the lower expansion part 11a.