  We present the earliest astronomical observation of a high energy neutrino
error box in which its variability was discovered after high-energy neutrinos
detection. The one robotic telescope of the MASTER global international network
(Lipunov et al. 2010) automatically imaged the error box of the very
high-energy neutrino event IceCube-170922A. Observations were carried out in
minute after the IceCube-170922A neutrino event was detected by the IceCube
observatory at the South Pole. MASTER found the blazar TXS 0506+056 to be in
the off-state after one minute and then switched to the on-state no later than
two hours after the event. The effect is observed at a 50-sigma significance
level. Also we present own unique 16-years light curve of blazar TXS 0506+056
(518 data set).
