This disclosure provides a device for preventing a toilet seat from being deviated left and right, the toilet seat comprises an upper cover (1) and a seat ring (2), locating members (3) are arranged at a bottom of the seat ring (2), the locating members (3) are installed at a bottom of the seat ring (2) through connecting pieces (4), each locating member (3) comprises a locating seat (31) and a locating piece (32) fixedly arranged on a side of the corresponding locating seat (31), the locating pieces (32) extend into the interior of the toilet bowl from the bottom of the seat ring (2) downwards, and the locating pieces (32) are adapted to engage with a left limit and/or a right limit of an inner side wall of the toilet bowl. This disclosure can effectively solve the problem that the seat ring (2) of an existing toilet is not fixed with the toilet bowl, and the condition of left-and-right deviation may occur, so that the experience feeling of the user when the toilet is used is better.