A resource allocating apparatus and a method for a Push-To-Talk (PTT) service in a wideband wireless communication system are provided. The method includes, when a Floor Grant message is received from a PTT server, allocating an uplink resource to a corresponding terminal and when a Floor Release message is received from the terminal, aborting the uplink resource allocation. The uplink resource is allocated only to the terminal having the data to be transmitted, and the resources are not allotted to terminals having no data to send.