A method and apparatus for allocating a radio resource in a wireless sensor network are provided, in which a signal requesting a radio resource allocation is received from any one of sensors included in the wireless sensor network, an amount of remaining energy is compared with respect to each zone where a sensor transmitting the signal is included, an order of zones, from a zone comprising a greatest amount of remaining energy to a zone having a least amount of remaining energy, is determined as a result of the comparison, and a time slot is allocated to a sensor of each zone according to the determined order of zones, when transmitting a frame for the radio resource allocation.