An apparatus for thermoforming plastic containers (2) comprising at least one thermoforming device (3) suitable for thermoforming a flat sheet (4) for making a container (2) equipped with an upper flange (5) projecting outward and at least one extracting device (6) associable with the thermoforming device (3) for extracting the thermoformed container (2) from it; when the extracting device (6) is associated with the thermoforming device (3) for extracting the already thermoformed container (2), the extracting device (6) and the thermoforming device (3) define a perimetric mould (7) suitable for hot bending the annular flange (5) of the already thermoformed container (2) before it is extracted from the thermoforming device (3).