Abstract: A bicycle indicator light includes left and right LEDs provided on a housing and oriented to illuminate an area on a left forward side and an area on a right forward side of the bicycle respectively, and a printed circuit board having a microcontroller unit, a gyro-specific IC and a driver IC. When the gyro-specific IC detects an inclination of the bicycle exceeding a predetermined angle to the left/right from an upright position of the bicycle, the gyro-specific IC sends an inclination signal to the microcontroller unit which directs the driver IC to drive the left/right LED to glow automatically.