We have studied 1/f noise in critical current I_c in h-BN encapsulated monolayer graphene contacted by NbTiN electrodes. The sample is close to diffusive limit and the switching supercurrent with hysteresis at Dirac point amounts to ≃ 5 nA. The low frequency noise in the superconducting state is measured by tracking the variation in magnitude and phase of a reflection carrier signal v_rf at 600–650 MHz. We find 1/f critical current fluctuations on the order of δI_c/ I_c≃ 10 ^{- 3} per unit band at 1 Hz. The noise power spectrum of critical current fluctuations SIc measured near the Dirac point at large, sub-critical rf-carrier amplitudes obeys the law SIc/Ic2=a/fβ where a≃ 4 × 10 ^{- 6} and β≃ 1 at f> 0.1 Hz. Our results point towards significant fluctuations in I_c originating from variation of the proximity induced gap in the graphene junction.