  We calculate the effective mass of a single quantized vortex in the BCS
superconductor at finite temperature. Using the effective action for a vortex,
we arrive at the mass formula as the integral of the spectral function
$J(\omega)/\omega^3$ over frequency. The spectral function is given in terms of
the transition elements of the gradient of the Hamiltonian between
Bogoliubov-deGennes eigenstates. We show that core-core, and core-extended
transitions yield the vortex mass, near T=0, of order of electron mass
displaced by the normal core. The extended-extended states contributions are
linearly divergent with the low frequency cutoff $\omega_c$, in accordance with
the Ohmic character of the spectral function at low energies. We argue that the
mass and friction are closely related in this system and arise from the same
mechanism - interaction with the surrounding fermionic degrees of freedom.
