An apparatus for thermoforming plastic containers comprising: a pickup station; a feeder for feeding flat sheets of thermoformable plastic material to the pickup station; at least one thermoforming device in turn comprising a shaped mould and a closing element, the shaped mould and the closing element being movable relative to each other at least between a home position in which they are away from one another, and a forming position in which they are near to each other for, in use, clamping a flat sheet between them; the closing element comprising a resting surface that is facing the shaped mould at least when they are in the forming position, and being equipped with suction means designed to retain on the resting surface at least one of said flat sheets at least when the shaped mould and the closing element are in the home position; one or more heating elements for heating the closing element; a transferring device for transferring the flat sheets from the pickup station to the closing element; an extracting device for extracting the thermoformed container from the shaped mould; and an electronic unit for controlling and checking operation of the apparatus; characterised in that said feeder comprises: at least one support for a reel of a web of said thermoformable plastic material; unwinding means for unwinding said reel of web, designed, in use, to feed the web along a sliding path extending from the at least one support to the pickup station; and a cutting device for cutting the web positioned along the sliding path for dividing the web into a plurality of pieces, each of which corresponds to one flat sheet to be fed to the pickup station. a pickup station; a feeder for feeding flat sheets of thermoformable plastic material to the pickup station; at least one thermoforming device in turn comprising a shaped mould and a closing element, the shaped mould and the closing element being movable relative to each other at least between a home position in which they are away from one another, and a forming position in which they are near to each other for, in use, clamping a flat sheet between them; the closing element comprising a resting surface that is facing the shaped mould at least when they are in the forming position, and being equipped with suction means designed to retain on the resting surface at least one of said flat sheets at least when the shaped mould and the closing element are in the home position; one or more heating elements for heating the closing element; a transferring device for transferring the flat sheets from the pickup station to the closing element; an extracting device for extracting the thermoformed container from the shaped mould; and an electronic unit for controlling and checking operation of the apparatus; at least one support for a reel of a web of said thermoformable plastic material; unwinding means for unwinding said reel of web, designed, in use, to feed the web along a sliding path extending from the at least one support to the pickup station; and a cutting device for cutting the web positioned along the sliding path for dividing the web into a plurality of pieces, each of which corresponds to one flat sheet to be fed to the pickup station.