An active device array substrate is provided. The active device array substrate includes multiple pixel structures, a drive circuit, multiple signal lines and a control line. The pixel structures are disposed in a display area. The drive circuit is disposed outside the display area. The signal lines are electrically connected to the drive circuit and the pixel structures corresponded to the signal lines. The control lines are intersected with the signal lines. A method adapted for inspecting defects on the active device array substrate is also provided. First, a tested signal line is selected from the signal lines, and the control line and the tested-signal line are conducted. Second, a test signal is input from the control line to the tested-signal line to determine a location of a defect. Finally, the control line and the tested signal line are isolated.