Abstract: A pillow that changes its height during lying on the back and lying sideways, automatically and reliably according to sleeping posture of a user. No adjustment is necessary, and the height is stable. A biasing device provided in a hollow of the head placement member of a pillow is equipped with a link mechanism including a load supporting link, a rear end side of which being placed slidably on an upper end portion of a rear side link and a front end side thereof being connected rotatably to a front end side of an upper side link, and a tension spring for biasing the load supporting link to push the same upwards.