Provided as an organogel formation agent for forming reverse wormlike micelles, and a thickening gel composition, are: an organogel formation agent that offers high safety for the body and environment, an agreeable usability, and favorable gelation ability； and a thickening gel composition using said organogel formation agent. Lecithin and an aliphatic carboxylic acid having 1 to 3 carboxyl groups or 0 to 2 hydroxy groups act as an organogel formation agent for forming reverse wormlike micelles of a variety of oils； using a three-component mixed system of the lecithin, the carboxylic acid, and a variety of oils, it is possible to obtain a thickening gel composition having a reverse wormlike micelle structure.
