Provided are an apparatus and method for broadcasting data, and an apparatus and method for broadcasting response data, of a sensor node in a beacon mode in a wireless sensor network system including a plurality of nodes. According to the apparatus and method for broadcasting data, an admission application message requesting an admission of a sensor node is transmitted to the wireless sensor network system, in which time-division time slots are assigned to each of the nodes of the wireless sensor network system, wherein, in the time-division time slot, the reception function of the node is activated and sensing data is transmitted; a beacon frame is received, which includes information that indicates a broadcasting time slot among the time-division time slots, wherein, in the broadcasting time slot, the reception function of each of the nodes of the wireless sensor network system having received the admission application message, is activated at the same time; and broadcasting data is transmitted during the broadcasting time slot. Accordingly, broadcasting data can be efficiently transmitted in a beacon mode of the wireless sensor network system.