In a surface acoustic wave resonator according to an embodiment, a quartz-crystal substrate includes an AT-cut 0° X-propagation first quartz-crystal substrate and a Z-cut second quartz-crystal substrate bonded over the first quartz-crystal substrate. A propagation direction of a surface acoustic wave in the second quartz-crystal substrate is inclined from an X-axis of a crystal by 27 to 33°, 87 to 93°, or 147 to 153°, and a thickness of the second quartz-crystal substrate is 0.2 to 1.0 times a wavelength of the surface acoustic wave.