A PH value detection device for detecting a PH value of a solution includes first and a second electrodes to be inserted into the solution; and a power source configured to apply a bipolar rectangular potential pulse signal to the first and second electrodes. A current detector is connected between the first and second electrodes and is configured to detect a current flowing through the first and second electrodes. A calculator is configured to calculate the PH value of the solution, based on the detected current.