The present invention relates to a mobile hearing aid having foldable earphones and howling prevention circuits mounted on headwear, including: a support member disposed on the inner periphery of the headwear and made of plastic or metal; and sensors provided on the surfaces of the earphones facingly covering a wearer's ears to detect the infrared radiation emitted from the human body, wherein hearing aid sounds are provided to the wearer when the earphones are covered on his or her ears and muted when the earphones are open from his or her ears, thereby preventing the occurrence of howling from the earphones open from his or her ears.