A headlamp control circuit reduces a possibility that all headlamps become lights-out in a two-lamp system headlight, even if a switching element fails under a high-beam condition while the single switching element is driven to light two right and left high-beam filaments. A headlamp control circuit includes switch sections (SW1) and (SW2) for lighting low-beam filaments (21) and (31), a switch section (SW3) for lighting high-beam filaments (22) and (32) together, a diode (D1) for detecting an output voltage on the switch section SW3, and a control section (120) for turning the switch section (SW3) to an on-condition in the case where a high-beam indication is accepted and for turning the switch sections (SW1) and (SW2) to an on-condition in the case where a low-beam indication is accepted and in the case where a high-beam indication is accepted and the diode (D1) detects no high-beam lighting voltage.