A wheelchair has two sides each provided with a side support frame, an armrest, and an armrest adjusting device. The side support frame has a front portion provided with a support rack, and a rear portion provided with a positioning bar pivotally connected with a rotation shaft, so that the side support frame may be pivoted about the rotation shaft. The rotation shaft is rotatably mounted in the support shaft of the wheelchair, so that the side support frame and the rotation shaft may be rotated about the support shaft. Thus, the side support frame may be rotated about the support shaft through a fixed angle, so that the side support frame may be rotated and moved to a rear portion of the backrest of the wheelchair, thereby facilitating the user entering and leaving the wheelchair.