An external electric field is still debatable for cancer treatment, although many study results proved its capacity. Cancer involves complex mechanisms, including how the cancer cells arise and grow. Thus, this disease is known to have many hallmarks. This condition complicates precise and accurate treatment. The study proved that an external electric field has prospects to become an effective cancer treatment, demonstrated by its ability to inhibit cancer growth through anti-proliferative and pro-apoptotic capacities. Several devices generating electric fields for cancer treatment were Tumour Treating Fields (TTFields), nanosecond Pulsed Electric Fields (nsPEF), picosecond Pulsed Electric Fields (psPEF), and Electro-Capacitive Cancer Therapy (ECCT). This article will compare those devices’ efficacy, safety, treatment methods, and research progress, including the advantages and disadvantages of static electric field devices and future research prospects. More attention will be focused on ECCT, which has been closely and profoundly investigated in breast cancer treatment.