The present disclosure illustrates a wearable body temperature monitoring device and a method thereof. The wearable body temperature monitoring device includes a hollow shell member and a circuit board. The hollow shell member includes a sensing surface and an outer surface opposite to each other, and the sensing surface is provided with hole. The circuit board is accommodated in the hollow shell member and includes a first side surface corresponding to the sensing surface and a second side surface corresponding to the outer surface. The circuit board is provided with a non-contact temperature sensor, a wireless transmission module, a processing unit, and a battery, and the non-contact temperature sensor is disposed at the first side surface and aligned with the hole of the sensing surface. The wearable body temperature monitoring device can respond the variation of the body temperature in real time when being attached on clothes.