Provided is a strip-shaped detector that detects an analyte in a liquid sample. The detector includes a collecting member that directly collects a liquid sample from a living organism, a holding member that holds a labeling reagent binding specifically to the analyte in a state where the labeling reagent can move along with the movement of the liquid sample, a detecting member to which a detection reagent is immobilized which captures a complex of the analyte and the labeling reagent by binding specifically to the analyte, an absorbing member that can absorb the liquid sample, and a liquid-impermeable supporting member, wherein the respective members are arranged on the supporting member in the longitudinal direction of the detector so that the liquid sample moves through the inside of these members, and the collecting member includes a protruding portion sticking out of the supporting member at the upstream side in the movement direction of the liquid sample.
