Magnetic resonance imaging provides a highly efficacity for the diagnosis of brain's disease. There are various methods to extract the required portions from MRI data. In this paper we propose a simple algorithm to carry out it by using vector quantization. Our porposed algorithm has three steps. First step is pixel classification using vector quantization. We classify image's pixel background, CSF (cerebrospinal fluid), gray matter and white matter. Second step, we obtain initial brain region using region mergering. Brain region consists of gray matter and white matter. Final step, we extracted brain region using location information and region size. We compare brain volume using proposed method in this paper with manually obtained brain volume by a doctor, and the difference for two methods is 0.1∼7.2%.