An object of the invention is to provide a plating pretreatment solution that can convert the surface of an aluminum substrate for hard disk devices into a surface suitable for electroless nickel plating, and a method for producing an aluminum substrate for hard disk devices using the same. The plating pretreatment solution of the present invention used for a plating pretreatment in production of an aluminum substrate for hard disk devices has an iron ion concentration of 0.1 g/l to 1.0 g/l and a nitric acid concentration of 2.0 wt % to 12.0 wt %. This plating pretreatment solution is used for a pretreatment of a plating step in which electroless nickel plating is applied to an aluminum substrate for hard disk devices. Accordingly, the surface of the aluminum substrate for hard disk devices is converted into a surface suitable for electroless Ni plating, and a smooth surface of a plated film is obtained by suppressing generation of waviness, nodules, and pits on the plated surface when electroless nickel plating is performed in the plating step.