Smartphone usage and the level of internet coverage in Indonesia are increasing rapidly every year. According to Ministry of Communication and Information of the Republic of Indonesia, more than 100 million of Indonesia's 250 million residents are active smartphone users in 2018. With such a large number, Indonesia is a country with the fourth most active smartphone users in the world after China, India and United States. In addition, the level of Indonesia's internet coverage in 2018 reached 82%. One of the most commonly used types of networks is ISM band network with frequency of 2.45 GHz. The number of smartphone and internet users in Indonesia currently encourages research on the effects of radio wave exposure on the human body tissue in relatively short and long time. Therefore, a study using smartphone antenna at resonant the frequency of 2.45 GHz against human head model is proposed. The study is aimed to evaluate how much the influence of 2.45 GHz frequency or Wi-Fi frequency on the human head in terms of specific absorption rate (SAR). This study is conducted by EM simulator software, which the human head is modeled as a homogenous head phantom consisting of three-layer human brain model. The human brain model is then fabricated as semisolid phantom, which is put in the 3-D printed human head container. The phantom is then exposed to the smartphone antenna for SAR measurement by using thermographic method. The result shows that the SAR values from 0.4585 W/kg to 1.4108 W/kg are obtained following exposure on the fabricated head phantom.