A stand adjustment device has a tripod-connecting member, a connecting seat, a proximal clamping plate, a boom-connecting tube, a locking shaft, and a manual operating member. The connecting seat is rotatably located around the tripod-connecting member. The proximal clamping plate is detachably attached to a side of the connecting seat. One end of the locking shaft is movably disposed in the boom-connecting tube. The boom is slidably mounted through the boom-connecting tube and the locking shaft. The locking shaft is slidably mounted through the boom-connecting tube, the proximal clamping plate, and the connecting seat such that the boom-connecting tube is rotatable relative to the connecting seat. The manual operating member and the locking shaft are configured to clamp the boom-connecting tube, the proximal clamping plate, and the connecting seat therebetween into a locked condition.