The invention relates to a circuit board testing device which comprises a base for bearing a motherboard to be tested, a fixed mount and a fixed side plate, wherein two lateral sides of the base are provided with a first strut and a second strut in opposite; the fixed mount can be fixed on the first strut and the second strut so as to clamp a to-be-tested signal adapter card inserted into the motherboard to be tested; one end of the fixed side plate is clamped on the base; and the other end is fixed on the second strut to support a first to-be-tested expansion card inserted into one side of the to-be-tested signal adapter card. The circuit board testing device can be used for conveniently and quickly testing various circuit boards.