A robot includes a main casing, a first spherical cap and a second spherical cap, and a shaft linking the spherical caps. The robot further includes a display, a first driving mechanism causing the first and second spherical caps to be rotated by the shaft, and a second driving mechanism that causes the main casing to be rotated. The robot also includes a control circuit and an electric power source, charged by electric power from an external charger. If the remaining electric power of the electric power source is lower than or equal to a predetermined value, the second driving mechanism is controlled to stop rotation of the main casing, and the first driving mechanism is controlled to switch a rotational direction of the first spherical cap and the second spherical cap, causing the display to be reciprocally moved in a vertical direction.