A coiled spring for a suspension device includes a lower seat winding section (42), an upper seat winding section (44), and a helical effective section (45) which is formed between the seat winding sections (42, 44). The lower seat winding section (42) includes: a first portion (42a) which is always in contact with a lower spring seat irrespective of a load; and a second portion (42b) which comes into contact with and separates from the lower spring seat according to a load. The wire diameter at the second portion (42b) is greater than the wire diameter at the first portion (42a) and is greater than the average wire diameter at the effective section (45). The upper seat winding section (44) includes: a third portion (44a) which is always in contact with an upper spring seat irrespective of a load; and a fourth portion (44b) which comes into contact with and separates from the upper spring seat according to a load. The wire diameter at the fourth portion (44b) is greater than the wire diameter at the third portion (44a) and is greater than the average wire diameter at the effective section (45).
