A suturing device for being inserted into and used in a body is disclosed. The suturing device includes a front arm that has string support portions supporting both ends of a surgical string, and a front guide portion attached to the string support portions and a back arm that has a needle-shaped member, a needle support portion supporting the needle-shaped member in a state of pointing to a predetermined first direction, and a back guide portion attached to the front guide portion 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 has a first guide groove guiding the needle-shaped member to one end of the surgical string supported by the string support portion and a second guide groove guiding the needle-shaped member.
