A post puller features a lifting member that is slidably disposed on a guide shaft and attachable to a lifting arrangement of a working machine. A pair of movable grippers are pivotally supported on the guide shaft at a fixed position therealong, and a pair of links are pivotally connected between the lifting member and the grippers. With a web or flange of the post received in a space between inner ends of the movable grippers, raising of the lifting member by the working machine lifts the outer ends of the movable grippers via the pair of links, thereby lowering inner ends of the grippers into closer proximity to one another to grip the web or flange of the post between the grippers. With the post gripped in this manner, further raising of the lifting member by the working machine pulls the post from the ground.