The invention relates to an adjustable umbrella-shaped inside support device for foundation ditch supporting construction, and belongs to the field of municipal engineering construction equipment. The invention adopts a sleeve-type supporting bar system consisting of two metal sleeves and movable supporting bars, the partial overlapping sleeving part of the sleeves forms a waist region with a telescopic middle part, the sleeve parts at both sides of the middle waist region form end regions, slideways are axially, symmetrically and uniformly distributed on the surfaces around the end regions, one end of each movable supporting bar is installed in the slideway by being connected and matched with a pulley, the extension and the shrinkage of the waist region are controlled, and the length of the waist region is adjusted, so as to satisfy the requirement for the main body support of a foundation ditch; the movable supporting bars are then matched and used, so that oblique extending supporting bars with different lengths and angles correspondingly extend out of sliding slots of the slideways at the end regions and extend to the circumference of the wall surface of the foundation ditch supported by the two end heads of the end regions, so as to form the multibar umbrella-shaped support within a certain radius range for the wall surface of the foundation ditch, thereby enhancing the supporting strength of the foundation ditch and improving the construction efficiency under the condition of ensuring safe construction.