An insertion apparatus for placing a packaging object in a packaging bag, the insertion apparatus comprising: a bag support unit that holds the packaging bag in a state where a bag mouth of the packaging bag is opened; a transfer mechanism that places the packaging object at a supply position; a first intermediate holding unit provided to be able to ascend and descend; an elevation mechanism that elevates or lowers the first intermediate holding unit so as to place the first intermediate holding unit at a first elevation position and a second elevation position; a first placement mechanism that moves the packaging object placed at the supply position in a horizontal direction so as to place the packaging object on the first intermediate holding unit placed at the first elevation position; a second placement mechanism that moves the packaging object, placed on the first intermediate holding unit at least partially placed in the packaging bag, in the horizontal direction so as to place the packaging object outside the first intermediate holding unit and inside the packaging bag, characterized in that the first intermediate holding unit includes: a base support part on which the packaging object is placed; and a first side guide part and a second side guide part between which the packaging object on the base support part is arranged, distance between the first side guide part and the second side guide part in regard to a horizontal direction being adjustable, and the insertion apparatus further comprises a first distance adjustment mechanism that adjusts the distance between the first side guide part and the second side guide part according to a position of the packaging object on the base support part; and a horizontal movement mechanism that moves the first intermediate holding unit placed at the second elevation position in the horizontal direction so as to insert at least a part of the first intermediate holding unit in the packaging bag via the bag mouth. a bag support unit that holds the packaging bag in a state where a bag mouth of the packaging bag is opened; a transfer mechanism that places the packaging object at a supply position; a first intermediate holding unit provided to be able to ascend and descend; an elevation mechanism that elevates or lowers the first intermediate holding unit so as to place the first intermediate holding unit at a first elevation position and a second elevation position; a first placement mechanism that moves the packaging object placed at the supply position in a horizontal direction so as to place the packaging object on the first intermediate holding unit placed at the first elevation position; a second placement mechanism that moves the packaging object, placed on the first intermediate holding unit at least partially placed in the packaging bag, in the horizontal direction so as to place the packaging object outside the first intermediate holding unit and inside the packaging bag, characterized in that the first intermediate holding unit includes: a base support part on which the packaging object is placed; and a first side guide part and a second side guide part between which the packaging object on the base support part is arranged, distance between the first side guide part and the second side guide part in regard to a horizontal direction being adjustable, and the insertion apparatus further comprises a first distance adjustment mechanism that adjusts the distance between the first side guide part and the second side guide part according to a position of the packaging object on the base support part; and a horizontal movement mechanism that moves the first intermediate holding unit placed at the second elevation position in the horizontal direction so as to insert at least a part of the first intermediate holding unit in the packaging bag via the bag mouth.