The radiation absorption distribution of electromagnetic energy into the breast phantom is of fundamental importance in understanding its therapeutic capability emitted by the microstrip applicator for non-invasive hyperthermia procedure. In this paper simple microstrip applicator with rectangular shape is presented. Different operating frequency were investigated to observe radiation absorption distribution, which is measured through specific absorption rate (SAR) parameter. The operational frequency was 915 MHz and 2450 MHz, the industry, scientific and medical (ISM) frequency range. As simulated by using the finite difference time-domain (FDTD) computational simulation which is known as SEMCAD X solver, the results shed an interesting observation on the SAR when frequency varies, which is shown by the transformation onto the penetration depth and focusing capability onto the breast area to be treated.