An endoscope comprising: an insertion portion including a distal end on a distal end side thereof and inserted into a body cavity; a treatment instrument insertion channel disposed in the insertion portion and adapted to communicate with the distal end; a treatment instrument elevator base rotatably provided to the distal end and having a wall portion projecting upward from a side portion the treatment instrument elevator base being adapted to elevate a first treatment instrument having a predetermined diameter and a second treatment instrument having a diameter greater than the predetermined diameter of the first treatment instrument, which are inserted into the treatment instrument insertion channel, in accordance with the operation of an operation portion; a first treatment instrument holding portion provided to the treatment instrument elevator base adapted to hold, at a first position, the first treatment instrument inserted into the treatment instrument insertion channel; a second treatment instrument holding portion provided to the treatment instrument elevator base adapted to hold, at a second position different from the first position, the second treatment instrument inserted into the treatment instrument insertion channel, the second treatment instrument being in contact with the wall portion without being inserted into the first treatment instrument holding portion; a contact portion in the form of an insulating block, provided at an opening portion of the treatment instrument insertion channel of the distal end adapted to sandwich the first treatment instrument elevated by the treatment instrument elevator base with the first treatment instrument holding portion in between, and adapted to sandwich the second treatment instrument elevated by the treatment instrument elevator base with the second treatment instrument holding portion in between; wherein a holding fixture portion is formed on the contact portion adapted to come in contact with the first treatment instrument held by a fixing portion of the treatment instrument elevator base and adapted to sandwich the first treatment instrument with the treatment instrument elevator base in between; characterized in that a leading portion provided to the contact portion and having a leading surface adapted to come in contact with and adapted to lead only the first treatment instrument elevated in accordance with a rotating movement of the treatment instrument elevator base to the holding fixture portion of the contact portion, without leading the second treatment instrument held at the second position and elevated in accordance with the rotating movement of the treatment instrument elevator base to the holding fixture portion. an insertion portion including a distal end on a distal end side thereof and inserted into a body cavity; a treatment instrument insertion channel disposed in the insertion portion and adapted to communicate with the distal end; a treatment instrument elevator base rotatably provided to the distal end and having a wall portion projecting upward from a side portion the treatment instrument elevator base being adapted to elevate a first treatment instrument having a predetermined diameter and a second treatment instrument having a diameter greater than the predetermined diameter of the first treatment instrument, which are inserted into the treatment instrument insertion channel, in accordance with the operation of an operation portion; a first treatment instrument holding portion provided to the treatment instrument elevator base adapted to hold, at a first position, the first treatment instrument inserted into the treatment instrument insertion channel; a second treatment instrument holding portion provided to the treatment instrument elevator base adapted to hold, at a second position different from the first position, the second treatment instrument inserted into the treatment instrument insertion channel, the second treatment instrument being in contact with the wall portion without being inserted into the first treatment instrument holding portion; a contact portion in the form of an insulating block, provided at an opening portion of the treatment instrument insertion channel of the distal end adapted to sandwich the first treatment instrument elevated by the treatment instrument elevator base with the first treatment instrument holding portion in between, and adapted to sandwich the second treatment instrument elevated by the treatment instrument elevator base with the second treatment instrument holding portion in between; wherein a holding fixture portion is formed on the contact portion adapted to come in contact with the first treatment instrument held by a fixing portion of the treatment instrument elevator base and adapted to sandwich the first treatment instrument with the treatment instrument elevator base in between; characterized in that a leading portion provided to the contact portion and having a leading surface adapted to come in contact with and adapted to lead only the first treatment instrument elevated in accordance with a rotating movement of the treatment instrument elevator base to the holding fixture portion of the contact portion, without leading the second treatment instrument held at the second position and elevated in accordance with the rotating movement of the treatment instrument elevator base to the holding fixture portion.