A visual acuity (VA) training device includes a guiding unit, an eye-movement sensor, and a controller. The guiding unit is configured to guide an eyeball to move towards multiple predetermined positions. The eye-movement sensor is configured to obtain multiple eye-movement signals according to movement of the eyeball. The controller obtains multiple eyeball muscle parameters according to the eye-movement signals, and the controller controls the guiding unit according to the eyeball muscle parameters, so as to adjust the predetermined positions.
