A device and a method of detecting a concentration of a sample are provided. The device includes a power supply unit configured to supply power to generate plasma, a plasma generation unit connected to the power supply unit and including a pair of electrodes facing each other, a plurality of signal detection units arranged on the pair of electrodes and configured to sense light emitted from the sample because of the plasma, and a controller configured to control a driving start point of the signal detection unit so that the signal detection unit is driven after a preset period of time after oscillation is terminated between the pair of electrodes.