Provided is a defoamer for a fermenter. A defoamer for a fermenter according to an embodiment of the present invention includes: a body (100) having a first hollow (110) at a central portion thereof and having a disk shape; a support (200) having a second hollow (210) connected with the first hollow (110), and extending from an upper surface (120) and a lower surface (130) of the body (100); and a plurality of first vanes (310, 320, 330, 340, 350, 360, 370, and 380) mounted on the lower surface (130) of the body (100).