To provide a seal structure for a fully hydraulic power steering control valve having excellent sealability with zero leakage by preventing a shaft and a backup ring portion form sliding against each other for small sliding resistance at all times, and also preventing the sliding resistance from varying even with pressure fluctuation within a housing.

The seal structure for the fully hydraulic power steering control valve comprises a shaft, a housing, a seal and a seal housing for retaining the seal. The seal housing is provided with the backup ring portion and the shaft and the backup ring portion are prevented from sliding against each other.