Provided is a knot formation device (10) which has a first arm mechanism (14a) and a second arm mechanism (14b). Needles (50, 51) are respectively fixed to both ends of a string-shaped member (L). When an arm body (36a) of the first arm mechanism (14a) rotates about an axial line (C4) while holding the needle (50), and an arm body (36b) of the second arm mechanism (14b) rotates about an axial line (C5) while holding the needle (51), a loop (R) can be formed in the string-shaped member (L). Next, the two arm mechanisms (14a, 14b) are brought closer to one another, and the two arm mechanisms (14a, 14b) transfer their respective needles (50, 51) to the other (14b, 14a). The two arm mechanisms (14a, 14b) each separate from the other (14b, 14a), and then a moving member (78) pushes the string-shaped member (L). Thereupon, a section in which the string-shaped member (L) is fixed to the needle (50) can be passed through the loop (R), and a knot (M1) can be formed in the string-shaped member (L). In this way, a knot (M1) can be formed automatically by a simple procedure.
