An apparatus (14) and method for guiding a cannon shell accurately are disclosed. The apparatus includes two main parts (21) adapted to be installed on the leading end of the cannon shell. The front main part of the apparatus is equipped with at least one pair of fins and is rotatable with respect to the rear main part. The pair of fins is controlled to hold the front main part substantially stable with respect to an external reference frame when the cannon shell rotates as it flies towards its target. Control system is comprised within the apparatus that receives location signals and is adapted to provide guiding control commands to the cannon shell via the fins so as to guide the shell accurately to its preprogrammed target. The control system is adapted to activate the detonation chain of the shell according to preprogrammed mode.