A power tool, such as a hammer drill (100), has first and second battery mount parts (160A, 160B) that are aligned in a longitudinal direction of the power tool. First and second batteries (170A, 170B) are mountable thereon in series along a straight line that extends in the longitudinal direction. The first battery (170A) is mounted on the first battery mount part (160A) by sliding along the straight line towards the second battery mount part (160B). The second battery (170B) is mounted on the second battery mount part (170B) by sliding along the straight line towards the first battery mount part (170A).