A battery apparatus and electronic equipment is capable of reliably mounting the battery apparatus on a battery mounting section, and advantageous in improving operability when mounting the battery apparatus on the battery mounting section. One surface of a case of a battery apparatus in a thickness direction is formed as a flat bottom surface. At the portions of the bottom surface on the both sides in a width direction, a plurality of engaging pieces are formed respectively so as to project outwardly in the width direction at spaced intervals in the length direction. The engaging pieces are arranged to engage with the engaging claws of the battery mounting section and position the positions in the thickness direction of the case in the battery mounting section, while mating the bottom surface of the case with the mounting surface of the battery mounting section of the electronic equipment and then sliding the case in the length direction of the case.