A fixing device for adjusting a telescoping arrangement comprises a seat disposed on an outer telescoping tube, a propelling arrangement disposed on the seat and inserted into limiting slots of an inner telescoping tube, a locking arrangement pivotally disposed on the seat to prop against the propelling arrangement, and a fastening arrangement fixing the locking arrangement to the seat. The movement of the locking arrangement toward the seat pushes the propelling arrangement to position the telescoping tubes, and concurrently an elastic member of the fastening arrangement springs against a fastening member of the fastening arrangement to make a fastening part of the fastening member lock with a fastened member which is disposed on the seat and thus position the locking arrangement, thereby preventing an unexpected slide of the telescoping tubes caused by touching the locking arrangement carelessly and increasing the use safety efficiently.