To provide a workpiece joining adjustment device capable of conveying workpieces in order at low cost without piling up workpieces in a joining part in a conveyance passage.

This workpiece joining adjustment device is provided with an arm support mechanism for holding a first arm and a second arm abutted on each of workpieces conveyed on a first conveyance passage and a second conveyance passage and each of the first and second arms turnably and energizing the arms to restore to an initial position crossing the direction of conveyance of the workpiece, a conveyance timing adjustment mechanism for regulating movement of either of the first and second arms to adjust conveyance timing of the workpiece when the other arm turns, and an abutting timing adjustment mechanism for staggering abutting timing on one side when a condition in which each workpiece conveyed in the first and second conveyance passages reaches the first and second arms substantially simultaneously is formed.