A pillow whose height can be automatically adjusted so that, when a user is in a face-up lying position, the back of the user's head is slightly higher than his or her back, and in addition, whose height can be automatically varied between a face-up lying position and a side lying position. A cavity section (8) is formed in a head placement member (3), and the cavity section (8) sags so that, when the head is placed on the pillow with the face up, the distance between the lowermost section of the head and a bottom member (2) is in the range of 10 - 30 mm. An urging mechanism (9) is placed in the cavity section, and the urging mechanism has X-shaped links (11) arranged in the cavity section (8), separated in the lateral direction. Each of the X-shaped links is constructed by pivotally connecting, by an intermediate link shaft (16), a first link member (12) sloping forwardly upward and a second link member (13) sloping backwardly upward. The urging mechanism further has a front side upper connection member (18) for connecting front end sections of the first members of both X-shaped links to each other, a back side upper connection member (20) for connecting rear end sections of the second link members of both X-shaped links to each other, and a spring member (21) for applying a spring force to both X-shaped links, the spring force acting in the direction that causes both link members of each X-shaped link to approach each other in the forward / backward direction along an action line in the forward / backward direction.