Present invention of vehicle's steering wheel rotation angle sensing device comprises, rotor rotating connected with steering shaft transmitting manipulation power to vehicle's wheel; main gear rotating connected with said rotor; first rotation gear and second rotation gear rotating with said main gear; first magnetic body and second magnetic body rotated in same rotation ratio with first rotation gear and second rotation gear connected with them individually, formed in hexahedral shape in which upper surface is larger than opposite bottom surface; first sensor and second sensor sensing phase change caused by rotation of said first magnetic body and second magnetic body; PCB substrate comprising said first sensor and second sensor and various terminals and pins; housing.By present invention it is possible to prevent magnetic body from moving freely to vertical direction without using adhesive agent, and to manufacturing angle sensing device without process of attaching the magnetic body to rotation gear, so total cost and time for manufacturing it also can be diminished.