A locking device for a stroller is provided. The stroller includes a pair of side frames and a base frame. The locking device comprises an articulated mechanism pivotally connected between the respective rear frames of the pair of side frames, a locking member slidably provided on the articulated mechanism for locking the articulated mechanism, and a pair of side braces pivotally connected to the locking member at one end thereof respectively and pivotally connected to the respective rear frames of the pair of side frames at the other end thereof. The folding and unfolding of the stroller can be easily carried out by means of the locking device.