A dual-mode crystal oscillator includes a single AT-cut quartz crystal piece, a package, and an integrated circuit. The integrated circuit includes an oscillation circuit configured to cause the AT-cut quartz crystal piece to oscillate at a frequency in the MHz band, a dividing circuit configured to divide the frequency in the MHz band to generate a frequency of 32.768 kHz, a selection circuit configured to select one of a pause state where the frequency in the MHz band is not output and an active state where the frequency in the MHz band is output. The mounting surface includes three electrodes arranged in a direction along the long side and two electrodes arranged in a direction along the short side. The electrode to output the frequency of 32.768 kHz and the electrode to output the frequency in the MHz band are arranged not adjacent to one another.