A bio-signal measurement parameter optimization method performed by a bio-signal measurement parameter optimization apparatus comprising a bio-signal measurer and a processor , the method comprising the steps of: emitting , by a light source , light onto a subject; measuring (804; 1510), by the bio-signal measurer comprising the light source and a photodetector , a bio-signal of the subject by detecting light that is reflected or scattered from the subject; determining (810; 1610), by the processor , a moving average (220; 312; 412) of the measured bio-signal (210; 311; 411); dividing , by the processor , the measured bio-signal (210; 311; 411) into sections ; comparing , by the processor , the determined moving average (220; 312; 412) to each value of bio-signal samples of the measured bio-signal (210; 311; 411) to determine whether each of the bio-signal samples satisfies a predetermined condition; determining , by the processor , a number of the bio-signal samples satisfying the predetermined condition, in each of the sections , based on a result of the determination of whether each of the bio-signal samples satisfies the predetermined condition; determining (1520; 1650), by the processor , a variance or a standard deviation of the determined number of bio-signal samples in each of the sections , as the bio-signal quality index; and adjusting , by the processor , a bio-signal measurement parameter, based on the determined bio-signal quality index, wherein the bio-signal measurement parameter comprises any one or any combination of an amount of the emitted light, an amplification gain of the measuring of the bio-signal, and a cancellation current of the measuring of the bio-signal, wherein a signal-to-noise ratio, SNR, of the measured bio-signal and the bio-signal quality index have a positive correlation. emitting , by a light source , light onto a subject; measuring (804; 1510), by the bio-signal measurer comprising the light source and a photodetector , a bio-signal of the subject by detecting light that is reflected or scattered from the subject; determining (810; 1610), by the processor , a moving average (220; 312; 412) of the measured bio-signal (210; 311; 411); dividing , by the processor , the measured bio-signal (210; 311; 411) into sections ; comparing , by the processor , the determined moving average (220; 312; 412) to each value of bio-signal samples of the measured bio-signal (210; 311; 411) to determine whether each of the bio-signal samples satisfies a predetermined condition; determining , by the processor , a number of the bio-signal samples satisfying the predetermined condition, in each of the sections , based on a result of the determination of whether each of the bio-signal samples satisfies the predetermined condition; determining (1520; 1650), by the processor , a variance or a standard deviation of the determined number of bio-signal samples in each of the sections , as the bio-signal quality index; and adjusting , by the processor , a bio-signal measurement parameter, based on the determined bio-signal quality index, wherein the bio-signal measurement parameter comprises any one or any combination of an amount of the emitted light, an amplification gain of the measuring of the bio-signal, and a cancellation current of the measuring of the bio-signal, wherein a signal-to-noise ratio, SNR, of the measured bio-signal and the bio-signal quality index have a positive correlation. <EOS>