The present invention provides a sound-transmitting membrane for a microphone, to be disposed to a sound-collecting opening of the microphone so as to allow sound to transmit through the membrane while preventing a foreign matter from entering into the microphone through the opening. This membrane for a microphone prevents the entry of a foreign matter, such as fine dust and water vapor, that is difficult for conventional sound-transmitting membranes to block, and ensures the microphone performance. This membrane for a microphone is composed of a nonporous film or a multilayer membrane including a nonporous film, has a surface density of 30 g/m2 or less, and has a sound transmission loss of less than 3 dB in a frequency range of 300 to 4000 Hz.