An osteosynthesis device that is both resorbable and radiopaque, produced using gradually degrading materials, includes at least one plate and a set of screws made of resorbable material, in which the plate consists of a composite mixture including i) a resorbable polymer or copolymer compound and ii) an inorganic filler that consists of at least one resorbable ceramic. The screws can be made of resorbable polymer, or of a composite mixture with at least one resorbable ceramic. The device is totally resorbable and radiopaque, and it offers a high level of safety, ensuring a strong and durable fixation of the screws to the plate and in the bone during the entire period needed for bone uniting.