An endoscope provided with a raising base (30, 30') comprising: a control body and an insertion portion extending from the control body; a raising-base accommodation recess formed in a distal-end proximal portion of the insertion portion; a treatment-tool insertion conduit formed in said insertion portion, a distal-end opening of said treatment-tool insertion conduit being communicably connected with said raising-base accommodation recess, and a flexible longitudinal treatment tool and guidewire being insertable said treatment-tool insertion conduit; and a raising base (30, 30') provided in said raising-base accommodation recess, said raising base (30, 30') being rotatable between a non-raised position and a maximum raised position about a rotational shaft extending in a widthwise direction of said insertion portion, wherein said raising base (30, 30') includes a treatment-tool support groove which extends in a longitudinal direction of said insertion portion; a pair of raising-base side walls positioned on either side of said treatment-tool support groove and opposing left and right inner side wall surfaces (23a, 23b) of said raising-base accommodation recess in said widthwise direction of said insertion portion; and an inner-to-outer communicably-connected groove provided in at least one of said pair of raising-base side walls, wherein said inner-to-outer communicably-connected groove is engagable with said guidewire and is not engagable with said treatment tool, said inner-to-outer communicably-connected groove communicably connecting an inner side of said at least one raising-base side wall with an outer side thereof, characterized in that said inner-to-outer communicably-connected groove comprises a pair of mutually opposing parallel groove walls (35a, 35b) forming a bottomed through-groove in a longitudinal direction of said rotational shaft, wherein opposing edges (35a2, 35b1) of said mutually opposing groove walls (35a, 35b) are configured to be directed in a downward direction when said raising base (30, 30') is positioned at said maximum raised position thereby frictionally engaging with said guidewire, without causing said guidewire to contact the inner side wall surfaces (23a, 23b) of said raising-base accommodation recess. a control body and an insertion portion extending from the control body; a raising-base accommodation recess formed in a distal-end proximal portion of the insertion portion; a treatment-tool insertion conduit formed in said insertion portion, a distal-end opening of said treatment-tool insertion conduit being communicably connected with said raising-base accommodation recess, and a flexible longitudinal treatment tool and guidewire being insertable said treatment-tool insertion conduit; and a raising base (30, 30') provided in said raising-base accommodation recess, said raising base (30, 30') being rotatable between a non-raised position and a maximum raised position about a rotational shaft extending in a widthwise direction of said insertion portion, wherein said raising base (30, 30') includes a treatment-tool support groove which extends in a longitudinal direction of said insertion portion; a pair of raising-base side walls positioned on either side of said treatment-tool support groove and opposing left and right inner side wall surfaces (23a, 23b) of said raising-base accommodation recess in said widthwise direction of said insertion portion; and an inner-to-outer communicably-connected groove provided in at least one of said pair of raising-base side walls, wherein said inner-to-outer communicably-connected groove is engagable with said guidewire and is not engagable with said treatment tool, said inner-to-outer communicably-connected groove communicably connecting an inner side of said at least one raising-base side wall with an outer side thereof, characterized in that said inner-to-outer communicably-connected groove comprises a pair of mutually opposing parallel groove walls (35a, 35b) forming a bottomed through-groove in a longitudinal direction of said rotational shaft, wherein opposing edges (35a2, 35b1) of said mutually opposing groove walls (35a, 35b) are configured to be directed in a downward direction when said raising base (30, 30') is positioned at said maximum raised position thereby frictionally engaging with said guidewire, without causing said guidewire to contact the inner side wall surfaces (23a, 23b) of said raising-base accommodation recess.