An angle adjuster for a bicycle seat that is disposed between a frame of a vehicle and a seat. The angle adjuster for a bicycle seat includes: a frame connector configured to be connected with the frame; a seat connector configured to support the seat, rotatably connected to the upper end of the frame connector, and having a nose at bottom facing the frame connector; an angle adjusting assembly disposed between the frame connector and the seat connector, and having a plurality of locking steps where the nose is configured to be selectively engaged to control rotational angle of the seat connector; an operating lever configured to be mounted on the frame to operate the angle adjusting assembly; and a wire connecting the angle adjusting assembly with the operating lever and reciprocating the angle adjusting assembly, when the operating lever is operated.