A headwear for electroencephalography is provided. The headwear includes a first arm to be attached to an area extending from a forehead or an occiput of a subject to a top of a head of the subject and configured to hold a first electroencephalogram electrode, a second arm connected to the first arm to be attached to a lateral side of the head of the subject and configured to hold a second electroencephalogram electrode, a third arm connected to the first arm to be attached to another lateral side of the head of the subject and configured to hold a third electroencephalogram electrode, a stretchable support member connectable to the first to third arms to cover at least a portion of the head in a direction toward the first arm, and at least one adjusting mechanism to adjust tightness of the first to third arms to the head.