In a surface acoustic wave resonator in which an IDT having electrode fingers for exciting surface acoustic waves is formed on a crystal substrate, the line occupying ratio causing the maximum electromechanical coupling coefficient and the line occupying ratio causing the maximum reflection of the surface acoustic waves in the IDT are different from each other, the center of the IDT has the line occupying ratio causing an increase in electromechanical coupling coefficient in comparison with the edges of the IDT, and the edges of the IDT have the line occupying ratio causing an increase in reflection of the surface acoustic waves in comparison with the center of the IDT.