An insertion system comprising: an insertion portion including at least a grasp portion, an elongated insertion portion to be inserted into a specimen not part of the present invention, and an insertion channel passing from the proximal end of the insertion portion to the distal end thereof; an insertion member to be inserted into the insertion channel; a first state detector which is disposed in the insertion portion and which detects information to calculate at least one of an insertion amount of the inserted insertion member in an insertion direction along a longitudinal direction of the insertion member and a rotation amount of the insertion member around its central axis along the insertion direction; and a calculation unit which calculates, from a detection result by the first state detector, operation support information to support in an insertion operation of the insertion member inserted through the insertion channel; characterized by: a first mark which is formed in an end face of an insertion hole of the insertion channel and which indicates a rotation reference position of the insertion member; and a second mark which is formed in the insertion member along the longitudinal direction of the outer circumferential surface thereof so that the direction and position of the second mark are adjusted to the direction and position of the first mark and which allows the insertion member to be disposed at a predetermined rotation reference position when the insertion member is inserted into the insertion channel. an insertion portion including at least a grasp portion, an elongated insertion portion to be inserted into a specimen not part of the present invention, and an insertion channel passing from the proximal end of the insertion portion to the distal end thereof; an insertion member to be inserted into the insertion channel; a first state detector which is disposed in the insertion portion and which detects information to calculate at least one of an insertion amount of the inserted insertion member in an insertion direction along a longitudinal direction of the insertion member and a rotation amount of the insertion member around its central axis along the insertion direction; and a calculation unit which calculates, from a detection result by the first state detector, operation support information to support in an insertion operation of the insertion member inserted through the insertion channel; characterized by: a first mark which is formed in an end face of an insertion hole of the insertion channel and which indicates a rotation reference position of the insertion member; and a second mark which is formed in the insertion member along the longitudinal direction of the outer circumferential surface thereof so that the direction and position of the second mark are adjusted to the direction and position of the first mark and which allows the insertion member to be disposed at a predetermined rotation reference position when the insertion member is inserted into the insertion channel. a first mark which is formed in an end face of an insertion hole of the insertion channel and which indicates a rotation reference position of the insertion member; and a second mark which is formed in the insertion member along the longitudinal direction of the outer circumferential surface thereof so that the direction and position of the second mark are adjusted to the direction and position of the first mark and which allows the insertion member to be disposed at a predetermined rotation reference position when the insertion member is inserted into the insertion channel.