An automatic replacement apparatus for a feed material, the automatic replacement apparatus comprising: a discharge unit configured to discharge a feed material to the outside; a pair of feed units disposed to be adjacent to the discharge unit and having a feed roll around which the feed material is wound; and a pair of material joint units respectively provided in the pair of feed units configured to connect a front end (Mf) of a first feed material waiting in a first feed unit, one of the pair of feed units, and an end (Me) of a second feed material being transferred from a second feed unit, the other of the pair of feed units, to the discharge unit in a butt joint manner, characterized in that the material joint unit includes: a support block including a front plate allowing the feed material to be disposed thereon and having a plurality of adsorption holes forming negative pressure; a clamp coupled to the front plate, one end of the clamp being hinged to one end of the front plate and the other end of the clamp being configured to be rotated and fixed to the other end of the front plate; and a separator accommodated in the front plate, one end of the separator being hinged to a central portion of the front plate and the other end of the separator being configured to rotate in an outward direction to protrude from the front plate. a discharge unit configured to discharge a feed material to the outside; a pair of feed units disposed to be adjacent to the discharge unit and having a feed roll around which the feed material is wound; and a pair of material joint units respectively provided in the pair of feed units configured to connect a front end (Mf) of a first feed material waiting in a first feed unit, one of the pair of feed units, and an end (Me) of a second feed material being transferred from a second feed unit, the other of the pair of feed units, to the discharge unit in a butt joint manner, characterized in that the material joint unit includes: a support block including a front plate allowing the feed material to be disposed thereon and having a plurality of adsorption holes forming negative pressure; a clamp coupled to the front plate, one end of the clamp being hinged to one end of the front plate and the other end of the clamp being configured to be rotated and fixed to the other end of the front plate; and a separator accommodated in the front plate, one end of the separator being hinged to a central portion of the front plate and the other end of the separator being configured to rotate in an outward direction to protrude from the front plate. a support block including a front plate allowing the feed material to be disposed thereon and having a plurality of adsorption holes forming negative pressure; a clamp coupled to the front plate, one end of the clamp being hinged to one end of the front plate and the other end of the clamp being configured to be rotated and fixed to the other end of the front plate; and a separator accommodated in the front plate, one end of the separator being hinged to a central portion of the front plate and the other end of the separator being configured to rotate in an outward direction to protrude from the front plate.