To provide an inexpensive door locking device for a plate-rack, a bookshelf, or the like with a simple mechanism in which lacking and unlocking is manually performed without using any battery.

A door locking device for a slate-rack, a bookshelf or the like, comprises a push-button device 2 to be fitted to a door side, and a receiver opening/closing device 3 to be fitted to a furniture body side. The push-button device 2 is provided with a receiving piece 23 projected to and fixed to a back side of a door 1, a push button 24 which is projected to a forward side of the door 1 and provided in an advancing/retracting manner, a push rod 25 which is fixed to the push button 24, pierced through the receiving piece 23, and formed in a rearwardly projected manner, and a spring member 26 to urge the push button 24 to the forward side of the door 1. A receiver opening/closing device 3 is provided with a slide shaft 33 which is engaged with the push rod 25 in an advancing/retracting manner, an intermediate gear 34 to be rotated as the slide shaft 33 is advanced/retracted, a hooking piece 35 which is opened/ closed as the intermediate gear 34 is rotated, and formed cable of being hooked to/detached from the receiving piece 23, and a spring member 36 to urge the slider shaft 33 forward.