To provide a slide fastener having fastener elements, lightweight and unlikely to be disengaged.

In the slide fastener (1), the fastener elements (10, 10', 30, 40) each include an element upper half section (11, 31, 41) and an element lower half section (21). The element upper half section (11, 31, 41) has a first tape holding portion (12, 32, 42), a tapered first head portion (13, 13', 33, 43), and a thin-walled portion (16, 36, 46) including a downward inclined surface (17, 37a, 37b, 47) downward inclined toward the end of the first head portion (13, 13', 33, 43), from a thin-walled starting portion (15, 35, 45) toward the first head portion (13, 13', 33, 43) which are provided in the element upper half section (11, 31, 41).