A dialysate-extracting apparatus is provided in which scattering of dialysate that may occur when an opening-and-closing device is detached from a collecting port can be prevented and the cleanliness of the collecting port can be assuredly maintained. The dialysate-extracting apparatus includes a dialysate-extracting device (10) connected to a dialysate flow route and having a collecting port (10d) from which dialysate flowing in the dialysate flow route is collectable, and an opening-and-closing device (H) detachable from and attachable to the dialysate-extracting device (10) in such a manner as to open and close the collecting port (10d) and including a seal portion (14a) that seals the collecting port (10d) in a closed state. When the opening-and-closing device (H) is detached from the dialysate-extracting device (10), a part of the opening-and-closing device (H) that is on an inner side with respect to the seal portion (14a) is bendable and displaceable toward the collecting port (10d).
