We report a case of a 7-month-old female with a dermoid cyst on the anterior fontanelle. She was born with a vacuum extractor. Two weeks later, her scalp on the anterior fontanelle bulged. A doctor was consulted when she was 3 months old, because the tumor was enlarging. Magnetic resonance image (MRI) showed a cystic mass on the anterior fontanelle. She was brought to our institute. At the first medical examination, she was alert and had no neurological deficit. The tumor was suspected to be a sinus pericranii or a pseudo meningocele. She was observed as an out patient, but the tumoral size become more enlarged. When she was seven months old, we punctured the cystic tumor and the tumor collapsed. But, two weeks later, it enlarged again. The cystic fluid was watery clear and the composition differed from cerebrospinal fluid (CSF). The tumor was resected totally. The histological examination revealed a dermoid cyst which involved ducts of the eccrine glands and folliculi pili. The cystic fluid was thought to be secreted from the eccrine glands.