Abstract: A work chair comprising a backrest, a seat-pan, a fastening mechanism, and a support leg. The backrest is provided with a first fastening device. Theseat-pan comprises a pelvic support and a thigh support. The pelvic support is provided on the underside thereof with a rotary fastening unit and is further provided on a longitudinal median thereof with a second fastening device. The fastening mechanism comprises a vertical fastening portion engageable with the first fastening device of the backrest for adjusting the backrest upwards and downwards. The fastening mechanism further comprises a horizontal fastening portion engageable with the second fastening device of the seat-pan for adjusting the longitudinal depth of the seat-pan. The support leg is provided with a rotary fastening member engageable with the rotary fastening unit of the seat-pan.