The present disclosure discloses a fixing device and a faucet installation device. The fixing device comprises a base and a pressing block mechanism. The pressing block mechanism comprises two pressing plates. The two pressing plates are respectively connected to a locking rod, and an inner side wall of the base protrudes to define two connecting bases. At least one of the locking rods is configured to move relative to the base between a working state and a movable state. Movement of the at least one of the locking rods between the working state and the movable state cooperates with the change of the pressing block mechanism between the unfolded state and the folded state.