Bicycle anti-lock braking device

A bicycle anti-lock braking device is connected to a brake caliper. The bicycle anti-lock braking device includes a casing, a control circuit board, a light-emitting component, a light guide, a driving component, and a depressurizing component. The casing has a first space and a second space separated from each other. The control board is located in the second space, and the control board has a first surface located opposite to the first space. The light-emitting component is located at the first surface of the control circuit board. The light guide is disposed through the casing, a part of the light guide is exposed to outside from the casing, and another part of the light guide is located in the second space and corresponds to the light-emitting component. The driving component is located at the first space of the casing and is electrically connected to the control circuit board. The depressurizing component is located at the first space of the casing. The depressurizing component is configured to be driven