A howling margin measuring device 20 comprises processing means 28 composed of gain controlling means 21 and a compressor 22 which are connected in series and controlling means 23. The gain controlling means 21 outputs an input sound signal after giving a gain thereto. If the level of a sound signal input to the compressor 22 is equal to or higher than a threshold level, the compressor 22 outputs the sound signal after compressing it with a specified ratio. The controlling means 23 is capable of controlling the gain of the gain controlling means 21 and reading the compression level of the compressor 22. The controlling means 23 reads the compression level of the compressor 22 while gradually increasing the gain of the gain controlling means 21, determines whether or not howling has been generated based on whether the read compression level has a value equal to or higher than a specified value, and calculates a howling margin based on the gain of the gain controlling means 21 when it is determined that howling has been generated.