A bicycle automatic shock absorbing device is provided. The bicycle automatic shock absorbing device includes a shock absorbing battery, a control chip, a sensor, and a driving module installed on a shock absorber. In operation, the control chip executes the automatic shock absorbing mode. The sensor detects shock impact and transmits a detection signal to the control chip. The control chip transmits an adjustment signal to the driving module, so that the driving module changes the damping response of the shock absorber. The control chip can determine and change the damping effect of the shock absorber to adapt to the road conditions while riding, so as to automatically adjust the damping of the shock absorber according to the road conditions.