An apparatus for replacing a welding tip of a spot welding gun, comprising: a post frame having a top surface on which a connection plate is provided; tip removal means combined with one side of the post frame at a specific location of the one side; and tip installing means combined with a top surface of the connection plate; wherein the tip removal means is configured to comprise: a main body combined with a specific location on one side of the post frame in a length direction; a cylinder installed at one end of the main body; and a tip removal unit combined with one end of the cylinder and placed to slide and move within the main body; wherein the main body is configured to comprise: a body comprising a base unit combined with the one side of the post frame, a protruded unit that is protruded and formed at one end of the base unit and that has a through hole formed at a central part of the protruded unit, and first and second extension units (128, 129) that are spaced apart from each other at a specific distance, protruded, and formed in a length direction of the body on one side of the base unit and that comprise a first through hole and a second through hole, respectively, at centers of the first and second extension units; a setting block that is combined with the base unit so that the setting block is placed between the first and the second extension units (128, 129) and that comprises a pair of stoppers on both sides of the setting block; and a cover combined with the body. a post frame having a top surface on which a connection plate is provided; tip removal means combined with one side of the post frame at a specific location of the one side; and tip installing means combined with a top surface of the connection plate; wherein the tip removal means is configured to comprise: a main body combined with a specific location on one side of the post frame in a length direction; a cylinder installed at one end of the main body; and a tip removal unit combined with one end of the cylinder and placed to slide and move within the main body; a main body combined with a specific location on one side of the post frame in a length direction; a cylinder installed at one end of the main body; and a tip removal unit combined with one end of the cylinder and placed to slide and move within the main body; wherein the main body is configured to comprise: a body comprising a base unit combined with the one side of the post frame, a protruded unit that is protruded and formed at one end of the base unit and that has a through hole formed at a central part of the protruded unit, and first and second extension units (128, 129) that are spaced apart from each other at a specific distance, protruded, and formed in a length direction of the body on one side of the base unit and that comprise a first through hole and a second through hole, respectively, at centers of the first and second extension units; a body comprising a base unit combined with the one side of the post frame, a protruded unit that is protruded and formed at one end of the base unit and that has a through hole formed at a central part of the protruded unit, and first and second extension units (128, 129) that are spaced apart from each other at a specific distance, protruded, and formed a setting block that is combined with the base unit so that the setting block is placed between the first and the second extension units (128, 129) and that comprises a pair of stoppers on both sides of the setting block; and a cover combined with the body.