This paper demonstrates nanoscale infrared thermal imaging in electrically biased bilayer graphene (BLG) by using a scattering-type scanning near-field optical microscope (s-SNOM). s-SNOM provides a noncontact technique to detect the thermally excited electromagnetic evanescent fields (∼21 THz) generated on the surface of a Joule-heated BLG. With increasing bias current, a strong near-field signal appears mainly in the sub-micrometer-sized constricted region. The temperature mapping of the graphene film can be derived from the infrared near-field signals, and shows good agreement with the finite-element simulation. Hence, we prove that s-SNOM is a potential infrared nano-thermography for the graphene device.