A device for preparing a cosmetic composition, comprising: - a base container delimiting an inner space able to receive a first cosmetic product, the inner space opening out through an insertion aperture; - a first cosmetic product, received in said inner space and formed by a plurality of deformable beads including a core and a frangible outer shell retaining the core; and - a mixing receptacle of the cosmetic composition, including a compression wall for compressing the first cosmetic product, intended to be mounted so as to be slideably mobile in the inner space through the insertion aperture between an outer position and an inner position for compressing the first cosmetic product, the compression wall comprising a lower bearing surface for bearing upon the first cosmetic product and delimiting a plurality of through-passages for circulating the first cosmetic product, the plurality of through-passages opening out into the inner space and the cross-section of each through-passage being less than 10% of a total section of the lower bearing surface of the compression wall; the device also comprising a side wall displaceable together with the compression wall, the side wall protruding from the compression wall and delimiting a mixing space into which the plurality of through-passages open out, and the side wall protruding out of the inner space of the base container when the compression wall of the receptacle occupies its inner position, characterized in that: the receptacle delimits at least one aperture for accessing the mixing space opening out towards the outside of the device when the compression wall occupies its inner position, the access aperture being distinct from the plurality of through-passages and, when the compression wall of the receptacle occupies its inner position, the access aperture remains clear. - a base container delimiting an inner space able to receive a first cosmetic product, the inner space opening out through an insertion aperture; - a first cosmetic product, received in said inner space and formed by a plurality of deformable beads including a core and a frangible outer shell retaining the core; and - a mixing receptacle of the cosmetic composition, including a compression wall for compressing the first cosmetic product, intended to be mounted so as to be slideably mobile in the inner space through the insertion aperture between an outer position and an inner position for compressing the first cosmetic product, the compression wall comprising a lower bearing surface for bearing upon the first cosmetic product and delimiting a plurality of through-passages for circulating the first cosmetic product, the plurality of through-passages opening out into the inner space and the cross-section of each through-passage being less than 10% of a total section of the lower bearing surface of the compression wall; the receptacle delimits at least one aperture for accessing the mixing space opening out towards the outside of the device when the compression wall occupies its inner position, the access aperture being distinct from the plurality of through-passages and, when the compression wall of the receptacle occupies its inner position, the access aperture remains clear.