A suturing device comprising: a sheath unit having a first long member and a second long member each having a distal end and a proximal end, the second long member being provided so as to be slidable in an axial direction with respect to the first long member; a suturing unit provided at a distal end of the sheath unit; and an operation unit provided at a proximal end of the sheath unit, wherein the suturing unit comprises a first arm connected to the distal end of the first long member and having a string support portion provided with an engagement member accommodating portion configured for releasably accommodating an engagement member (6a, 6b) provided at an end portion of a surgical string, and a second arm having a needle-shaped member, provided so as to be slidable with respect to the first arm, and connected to the distal end of the second long member, and the operation unit comprises a first operation portion connected to the proximal end of the first long member, and a second operation portion connected to the proximal end of the second long member and provided so as to be slidable with respect to the first operation portion, characterized in that the operation unit further comprises slide regulation means (41d, 42d, 43, 43')(41h, 42h, 44)(45, 42i) for releasably fixing the first operation portion and the second operation portion in a state where the first operation portion and the second operation portion are disposed such that a halted state occurs where a distal end portion (52a4) of the needle-shaped member is in the engagement member accommodating portion or at a position where the distance from a surface at the proximal end of the string support portion is 3 mm or less without engagement with the engagement member (6a, 6b). a sheath unit having a first long member and a second long member each having a distal end and a proximal end, the second long member being provided so as to be slidable in an axial direction with respect to the first long member; a suturing unit provided at a distal end of the sheath unit; and an operation unit provided at a proximal end of the sheath unit, wherein the suturing unit comprises a first arm connected to the distal end of the first long member and having a string support portion provided with an engagement member accommodating portion configured for releasably accommodating an engagement member (6a, 6b) provided at an end portion of a surgical string, and a second arm having a needle-shaped member, provided so as to be slidable with respect to the first arm, and connected to the distal end of the second long member, and a first arm connected to the distal end of the first long member and having a string support portion provided with an engagement member accommodating portion configured for releasably accommodating an engagement member (6a, 6b) provided at an end portion of a surgical string, and a second arm having a needle-shaped member, provided so as to be slidable with respect to the first arm, and connected to the distal end of the second long member, and the operation unit comprises a first operation portion connected to the proximal end of the first long member, and a second operation portion connected to the proximal end of the second long member and provided so as to be slidable with respect to the first operation portion, characterized in that the operation unit further comprises slide regulation means (41d, 42d, 43, 43')(41h, 42h, 44)(45, 42i) for releasably fixing the first operation portion and the second operation portion in a state where the first operation portion and the second operation portion are disposed such that a halted state occurs where a distal end portion (52a4) of the needle-shaped member is in the engagement member accommodating portion or at a position where the distance from a surface at the proximal end of the string support portion is 3 mm or less without engagement with the engagement member (6a, 6b). a first operation portion connected to the proximal end of the first long member, and a second operation portion connected to the proximal end of the second long member and provided so as to be slidable with respect to the first operation portion, characterized in that the operation unit further comprises slide regulation means (41d, 42d, 43, 43')(41h, 42h, 44)(45, 42i) for releasably fixing the first operation portion and the second operation portion in a state where the first operation portion and the second operation portion are disposed such that a halted state occurs where a distal end portion (52a4) of the needle-shaped member is in the engagement member accommodating portion or at a position where the distance from a surface at the proximal end of the string support portion is 3 mm or less without engagement with the engagement member (6a, 6b).