The invention discloses a fixing device for a smartphone. The fixing device comprises the smartphone, a suction cup, a first connecting seat, a mobile phone clamping device, a rotating device, a firstlocking screw, a first fixing seat, a moving column, a tension spring, a fixing sleeve, a second connecting seat, a second locking screw, a second fixing seat, a locking nut, a screw rod, a second fixing seat, a cover body, a connecting piece and an adjusting nut. The structure is reasonable and simple, the production cost is low, and mounting is convenient. During using, the smartphone is placedinto a shell of the clamping device firstly, the bottom of the smartphone is located in a fixing clamping claw, meanwhile, a left clamping claw is leftwards pulled out to enable the smartphone to belocated in the left clamping claw, through an arranged gear set, when the left clamping claw is pulled out, a right clamping claw also moves towards the right side simultaneously, thus the smartphoneis advantageously placed in; and in addition, a movable magnetic block and a fixed magnetic block are arranged, the need of temporary fixing use of the smartphone is met, and thus the using requirements of people under different situations are met.