The invention relates to a tuning-fork type crystal resonator in which the frequency adjustment accuracy is increased, and a frequency adjustment method thereof. In a tuning-fork type crystal resonator having a tuning-fork shaped piece of quartz crystal in which a pair of tuning fork arms extend from a tuning fork base, and a frequency adjustment method thereof, there is provided a first frequency adjustment step for adjusting an oscillation frequency by forming inclined surfaces spanning from outer peripheral surfaces surrounding the pair of tuning fork arms toward distal end surfaces, by using a femtosecond laser irradiated in a direction from the outer peripheral surfaces toward the distal end surfaces, or in a direction from the distal end surfaces toward the outer peripheral surfaces.