A biological information detector includes a wristband, a housing, an opening, a light-emitting part, a reflecting part, a light-receiving part, and a protecting part. The opening is defined in a surface of the housing adapted to face a surface of the wrist of the user. The light-emitting part is disposed inside the housing and configured to emit green light. The reflecting part is disposed in periphery of the light emitting part, and configured to reflect the light emitted by the light-emitting part, wherein the reflecting part is disposed inside the housing. The light-receiving part is disposed inside the housing, and configured to receive reflected light reflected at a detection site of the wrist of the user. The protecting part is configured to protect the light-emitting part and the reflecting part, and is disposed at the opening of the housing to contact with the detection site.