To provide a door safety device that detects the retreat of a safety shoe without need for a cable and special fabrication.

In the door safety device, a detecting means 7 for detecting the retreat of the safety shoe 6 protrudingly installed at the front edge of a door 4 moving horizontally is disposed at the top of the safety shoe 6. The door safety device includes: a light projecting part 7a for projecting a light beam 7c horizontally in the open/close direction of the door 4, and a light receiving part 7b for receiving the light beam 7c projected from the light projecting part 7a. The safety shoe 6 is configured to retreat and move upward caused by the contact with an obstacle. The safety shoe 6, upon contacting with the obstacle, retreats and moves upward, causing the upper end of the safety shoe to block the light beam 7c. This enables control means to detect the retreat of the safety shoe 6.

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