[Object] To provide a suturing device for suturing an internal body tissue in a short period of time.[Solving Means] There is provided a suturing device for being inserted into and used in a body. The suturing device includes a front arm 51 that has string support portions 51a supporting both ends of a surgical string 6, and a front guide portion 53 attached to the string support portions 51a； and a back arm 52 that has a needle-shaped member 52a, a needle support portion 52b supporting the needle-shaped member 52a in a state of pointing to a predetermined first direction, and a back guide portion 52c attached to the front guide portion 53 such that the back guide portion is capable of sliding in a direction substantially parallel to the first direction, and rotating around an axis substantially parallel to the first direction. The front guide portion 53 has a first guide groove 53e guiding the needle-shaped member 52a to one end 6a of the surgical string 6 supported by the string support portion 51a, and a second guide groove 53e guiding the needle-shaped member 52a to the other end 6b of the surgical string 6, when the back arm 52 slides in the first direction.
