An inertia measure unit (IMU) includes a main circuit board, and first and second weight blocks. A first surface of the first weight block contacts the main circuit board. The first weight block includes a recess formed on a second surface thereof opposite to the first surface, and an opening formed on a side surface thereof. The second weight block is coupled to the first weight block on the second surface to cover the recess. The first and second weight blocks jointly form an inner chamber in communication with the opening. The IMU further includes a circuit board disposed in the inner chamber, and a signal line coupled to an edge of the circuit board and extending out of the opening. The signal line bends over an outer surface of the first weight block or the second weight block to connect to the main circuit board.