The utility model relates to a double-end automatic machining machine for valve rods. The double-end automatic machining machine comprises a main machine platform, a carriage mechanism, a spindle mechanism, a feeding mechanism, a cutter rest and a control mechanism. The spindle mechanism is a double-end automatic clamping device, and the carriage mechanism is composed of a left carriage and a right carriage which are arranged on the two sides of the spindle mechanism. The double-end automatic clamping device is composed of a spindle head, a spindle, an expansion chuck and a clamping piston, wherein the clamping piston is provided with an inner hole with the diameter the same as the diameter of a small round hole of the spindle, the external circular surface of the expansion chuck is in movable fit with the inner hole of the clamping piston and an inner hole of the spindle, and horn-shaped external circular conical surfaces at the two ends of the expansion chuck are matched with an internal circular conical surface of the end portion of the inner hole of the clamping piston and an internal circular conical surface of the end portion of the inner hole of the spindle respectively. A piston cavity of the clamping piston is communicated with a hydraulic system through an oil inlet and an oil outlet which are formed in the spindle head. By means of the double-end automatic machining machine, the two ends of each valve rod can be machined at the same time. The double-end automatic machining machine has the advantages that the machining efficiency is high, and the concentricity of external circles at the two ends of each valve rod is good. Accordingly, the double-end automatic machining machine is suitable for cutting the external circles at the two ends of each valve rod.