Chair whose seat swings in a front-rear direction and a left-right direction

A chair, wherein a seat swings in front-rear and left-right directions with respect to a support base, the chair is configured such that swinging of the seat in the front-rear direction with respect to the support base is capable of being suppressed at one or a plurality of predetermined positions, or arbitrary position via an operation of an operation member, the chair comprising:

• an engaged part provided at a support base side or a seat side, the engaged part comprising a front-rear direction groove part extending in the front-rear direction and a left-right direction groove part extending in the left-right direction, the front-rear direction groove part crossing the left-right direction groove part to form a center crossing part where a groove depth is deeper than any other portion of the front-rear direction groove part and the left-right direction groove part, and
• an engaging part that engages the engaged part at the support base side or the seat side, the engaging part provided at the seat side or the support base side, and the engaging part at the seat side or the support base side elastically protruding toward the engaged part at the support base side or the seat side by the operation of the operation part, wherein the engaging part engages one of the front-rear direction groove part or the left-right direction groove part of the engaged part in accordance with swinging of the seat to the front-rear and left-right directions and swinging to one direction is regulated, and then, by further swinging to another direction, whereby the engaging part engages the crossing part and swinging in both front-rear and left-right directions is regulated.