To provide a weight mounting device for reducing labors to mount a weight to a front part of a tractor.

This device comprises a mounting frame 25 mounted to a tractor 1, a weight mounting frame 23 mounted to a weight 22, and an elevating means 24 for elevating the weight mounting frame 23. Engagement parts 28, 29 are provided to the mounting frame 25, and engaged parts 36, 37 are provided to the weight mounting frame 23. The weight mounting frame 23 is raised by the elevating means 24, and the engaged parts 36, 37 of the weight mounting frame 23 are engaged with the engagement parts 28, 29 of the mounting frame 25. A lock means 26 is provided to be locked in a manner that the engaged parts 36, 37 are not separated from the engagement parts 28, 29 under such a condition.