Transcranial electrical stimulation (tCES) is a non-invasive and safe treatment, which uses a low direct current or alternating current to change the excitability of the cerebral cortex. The tCES has been applied in clinical trials related to rehabilitation research in recent years, and the safety and effectiveness have also been established. However, the existing tCES products effect on the whole brain networks and lack special waveforms. The investigators developed a wearable high-definition tCES (HD-tCES) with special waveforms. This novel stimulation system will result in more precise and focal stimulation of selected brain regions with special waveforms to display better neuromodulation performance. In this study, the investigators will preliminarily examine the effects and safety of the HD-tCES in patients with fibromyalgia. The investigators expect that the HD-tCES will relief pain, improve sleep quality, emotion, and general health of the patients.

Inclusion Criteria:

1. With a diagnosis of fibromyalgia.
2. Age ≥ 20 years.
3. A mean pain score ≥ 4 on a 11-point numeric rating scale during the 2 weeks preceding the trial.

Exclusion Criteria:

1. Intolerance to electrical stimulation.
2. A history of arrhythmia.
3. Implantable medical electronic devices (e.g., like pacemaker).
4. Metal implants in the head or neck.
5. Wounds on the skin of head.
6. A history of brain surgery or severe brain trauma.
7. Severe cognitive or psychiatric disorders (e.g., schizophrenia, depression or bipolar disorder).
8. A history of seizure or other brain pathology.
9. Drug or alcohol abuse.
10. Malignant neoplasm or rheumatism disorder (e.g., SLE, RA, AS, IBD)
11. Pregnancy.
12. Change in medication of fibromyalgia within 1 week prior the trial.
13. Pregnant or breastfeeding women.
14. Intra-cerebral lesions (such as brain tumors, arteriovenous tumors).
15. History of encephalitis or meningitis.