An insertion assisting tool for an endoscope comprising: a tubular body having a passage through which an insertion part of an endoscope is passed; a sidewall opening part provided in a distal end of a sidewall portion of the tubular body, a distal end portion of the insertion part being capable of passing through the sidewall opening part; and a guiding member disposed in the passage and having a guiding surface guiding the insertion part inserted into the passage to the sidewall opening part, wherein the guiding member is a movable guiding member capable of transition between an inclined state where the guiding surface is obliquely inclined relative to an axial direction of the tubular body and a retracted state where the guiding surface is made substantially parallel to the axial direction of the tubular body, the guiding surface is capable of guiding the insertion part to the sidewall opening part in the inclined state, and the guiding surface is configured to be rotatable between the inclined state and the retracted state around a supporting part (88, 84) which is supported on the sidewall portion of the tubular body and the supporting part (88, 84) defining a supporting axis, the supporting axis of the guiding member is at a more proximal axial position than the distal end of the sidewall opening part of the tubular body, a manipulating wire for switching of the guiding member between the parallel state and the inclined state by applying a tractive force, characterized in that the supporting axis of the guiding member is positioned in closer vicinity of the side wall opening part than the longitudinal axis of the tubular body with respect to the radial direction of the tubular body; the end portion of a side opposite to the supporting part of the guiding surface of the guiding member comes in contact with an inner surface of the sidewall portion on a side opposite to the sidewall opening part of the tubular body only in the inclined state; urging means are provided, adapted to urge the guiding surface of the guiding member in the inclined state or in the retracted state, unless the tractive force is applied to the guiding member by the manipulating wire, and the supporting part (88, 84) includes: shaft pins as the supporting axis; and shaft receiving members configured to rotatably support the shaft pins, wherein the urging means includes a helical torsion coil spring disposed between the shaft receiving members and the shaft pins. a tubular body having a passage through which an insertion part of an endoscope is passed; a sidewall opening part provided in a distal end of a sidewall portion of the tubular body, a distal end portion of the insertion part being capable of passing through the sidewall opening part; and a guiding member disposed in the passage and having a guiding surface guiding the insertion part inserted into the passage to the sidewall opening part, wherein the guiding member is a movable guiding member capable of transition between an inclined state where the guiding surface is obliquely inclined relative to an axial direction of the tubular body and a retracted state where the guiding surface is made substantially parallel to the axial direction of the tubular body, the guiding surface is capable of guiding the insertion part to the sidewall opening part in the inclined state, and the guiding surface is configured to be rotatable between the inclined state and the retracted state around a supporting part (88, 84) which is supported on the sidewall portion of the tubular body and the supporting part (88, 84) defining a supporting axis, the supporting axis of the guiding member is at a more proximal axial position than the distal end of the sidewall opening part of the tubular body, a manipulating wire for switching of the guiding member between the parallel state and the inclined state by applying a tractive force, characterized in that the supporting axis of the guiding member is positioned in closer vicinity of the side wall opening part than the longitudinal axis of the tubular body with respect to the radial direction of the tubular body; the end portion of a side opposite to the supporting part of the guiding surface of the guiding member comes in contact with an inner surface of the sidewall portion on a side opposite to the sidewall opening part of the tubular body only in the inclined state; urging means are provided, adapted to urge the guiding surface of the guiding member in the inclined state or in the retracted state, unless the tractive force is applied to the guiding member by the manipulating wire, and the supporting part (88, 84) includes: shaft pins as the supporting axis; and shaft receiving members configured to rotatably support the shaft pins, wherein shaft pins as the supporting axis; and shaft receiving members configured to rotatably support the shaft pins, wherein the urging means includes a helical torsion coil spring disposed between the shaft receiving members and the shaft pins.