Abstract: The invention relates to a device (1) for forming an insole, able to be introduced into a shoe. It also relates to a shoe equipped with such a device. This device (1) comprises: two modules (2, 3) made of thermoformable material which is flexible, elastic and fluid-tight, such as to gas, liquid or gel, said modules consisting of at least one cavity (6, 7) able to contain said fluid; at least one channel (8) connecting at least two cavities. At least one duct (11) is arranged on the module in order to inject into or evacuate from the cavity a quantity of fluid, such as gas, liquid or gel (16) located inside the cavity.