A detector for liquid chromatography has light sources that generate light in an ultraviolet region and in a near-infrared region; a flow cell, through which sample liquid flows; an optical system to let light generated from the light sources become incident on the flow cell concurrently; a detection element that detects light in the ultraviolet region that passes through the flow cell; a detection element that detects light in the near-infrared region that passes through the flow cell; and an arithmetic operation part that performs arithmetic operation of a first signal value obtained from the detection element and of a second signal value obtained from the detection element. The arithmetic operation part combines the first signal value and the second signal value to calculate a signal value with a reduced baseline fluctuation resulting from a mobile phase during a gradient analysis.