To provide a vehicle assistant grip mounting structure assuring supporting rigidity of an assistant grip and avoiding or reducing the influence of an impact load a preset value or higher given from the side of a body on an occupant head.

An assistant grip supporting member 20 has a top 21 having assistant grip mounting portions 21A, 21B, an upper face 13 in a bent form on the top 21 with its upper edge joined to a side rail inner 11 and a lower face 14 in a bent form on the top 12, and the lower face 14 is provided with lower flanges 27a-27d to be jointed to lower flanges 14a, 18a of a side rail 10 and shock absorbing portions 24, 25 formed corresponding to the assistant grip mounting portions 21A, 21B. The assistant grip supporting member 20 is used for mounting the assistant grip 30 on the side rail inner 11.