A discharge lamp driver includes a discharge lamp drive unit, a control unit, and a voltage detection part. When an inter-electrode voltage is smaller than a first predetermined value, the control unit controls the discharge lamp drive unit to provide a mixed period in which a first period and a second period are alternately repeated and a third period alternately including a first direct-current period and a second direct-current period. A length of the first direct-current period is larger than a length of the second direct-current period. The length of the second direct-current period is smaller than 0.5 ms. A total of the lengths of the first direct-current periods in the third period is larger than a length of the second period. When the inter-electrode voltage is smaller than the first predetermined value, the control unit is configured to increase the length of the third period in a stepwise manner.