In at least one embodiment of the disclosure, a driving device for a discharge lamp includes an alternating current supply section and a frequency switching section. The alternating current supply section supplies two electrodes of the discharge lamp with an alternating current. The alternating current includes a plurality of modulation periods with each modulation period including a highest frequency term and a lowest frequency term. The frequency switching section varies a frequency of the alternating current non-monotonically between the highest frequency term and the lowest frequency term of the modulation period in response to a predetermined condition being satisfied.