This paper describes the development of a muscle-equivalent phantom for electrical impedance tomography (EIT). Conventional phantom adding titanium dioxide coated with antimony-doped tin oxide (ATO/TiO2) cannot mimic the electrical properties of the human body over wide frequency band. The main material of the ATO/TiO2-added phantom was changed from water to glycerol, and polyethylene powder (PEP) was added to decrease the relative permittivity of the medium, in order to expand the frequency band that can be mimicked. The electrical properties were measured for varying additions of glycerol, PEP and ATO/TiO2, and the results agreed with the theoretical equations. Muscle-equivalent phantom for 10 kHz to 10 MHz were developed, and the errors in the electrical properties were 8.55% and −7.14% for relative permittivity and conductivity, respectively. The combination of a development phantom with a skin-equivalent phantom and a fat-equivalent phantom allows for more accurate evaluation of EIT devices.