An insertion system for electrical conductors is provided that can widen the gap between insulating paper. An insertion system (1) includes: a first moving part (4) that causes a leg of the coil element (10) to move in an insertion direction of a slot (16); a guide part (3) that guides the leg into the slot (16); and a pair of first spreader plates (7A) and a pair of second spreader plates (7B) that can spread at a leading end side thereof, in which these pairs of spreader plates are formed so as to extend inclined relative to the insertion direction so as to approach each other towards a leading end side, and a gap therebetween is narrower than a width of insulating paper (17) at the leading end side, and is wider than a width of the leg of the coil element (10) at a base end side.