According to an embodiment, a synchronization variable monitoring device includes: an address comparator configured to compare a received address included in an Invalidate Request, and an address that is set as an address of synchronization variable data upon receiving the Invalidate Request; a readout circuit configured to read out data of the address of the synchronization variable data when the received address and the address of the synchronization variable data coincide with each other; a conditional variable comparator configured to determine whether or not a predetermined condition is satisfied based on the data read out by the readout circuit; and a synchronization completion flag register configured to output a synchronization signal indicating that a synchronization condition is satisfied when the conditional variable comparator determines that the predetermined condition is satisfied.