The present invention relates to a hydraulic breaker. The valve is installed on an inner surface of the cylinder bush and the cylinder inner diameter portion to be movable in the vertical direction. The valve includes an upper valve portion having an upper end surface on which the pressure of the upper cylinder chamber acts, a lower valve portion having a lower end surface on which the pressure of the upper cylinder chamber acts, a first valve expanded-diameter portion which is formed between the upper valve portion and the lower valve portion, of which an outer diameter expands to be greater than outer diameters of the upper valve portion and the lower valve portion, and in which a first upper valve hydraulic pressure area communicates with the first and second flow channels, and a second valve expanded-diameter portion which is formed between the first valve expanded-diameter portion and the lower valve portion, of which an outer diameter expands to be greater than an outer diameter of the first valve expanded-diameter portion, and in which the second upper valve hydraulic pressure area communicates with the fourth flow channel, and the pressure of the valve switching chamber acts on a lower valve hydraulic pressure area having an area greater than an area of the first upper valve hydraulic pressure area.