An infrared detector may be configured to detect a wide bandwidth of infrared spectrum using a broadband surface plasmon resonator. The infrared detector may include a substrate; a thermistor member disposed spaced from the substrate, the thermistor member having a resistance value that varies according to temperature; a resonator disposed on the thermistor member, the resonator configured to generate surface plasmon resonance; a pair of thermal legs configured to support the thermistor member such that the thermistor member is disposed spaced from the substrate; and a pair of conductive lead wires respectively disposed on the pair of thermal legs. The conductive lead wires may be configured to transmit signals to the substrate from the thermistor member and the resonator. The resonator may have a plurality of resonant frequencies and be configured to generate the surface plasmon resonance in a plurality of resonant modes.