Reported is femtosecond laser direct patterning of sensing materials toward flexible integration of micronanosensors (FIMS), meaning the capability to fabricate multiple functional sensors of smaller size on a nonflat surface of a substrate that is not limited to silicon. As a representative example, a photosensitive $\mathrm{Sn}{\mathrm{O}}_2$ colloidal solution (sol) was developed, from which complex micronanostructures were written via a two-photon absorption process. After thermal decomposition of organic components, the patterned $\mathrm{Sn}{\mathrm{O}}_2$ microsensors responded to relative humidity (RH) with a variation range of 5 orders of magnitude. FIMS would open a new door for miniaturization of micronanosensors expected in intelligent microsystems.