In a directional control device for a solenoid valve assembly, connection ports 4 and 5 of a supply/exhaust block 2 and connecting sections 19 and 20 of a manual directional control valve 3 are connected together using a fixing bracket inserting groove 17 cut to cross opposite sides of a connection port train and a generally U-shaped fixing bracket 18 inserted in the fixing bracket inserting groove 17. Locking grooves 19a and 20a are cut in peripheries of the connecting sections 19 and 20 in which the fixing bracket 18 is locked. Ports 6 and 8 of the manual directional control valve 3 are connected to pipe joints 21 inserted therein by the same connection structure as that which connects the connection ports 4 and 5 and the connecting sections 19 and 20 thereby enabling the pipe joints 21 to be mounted on the connection ports 4 and 5 of the supply/exhaust block 2 in place of the directional control valve 3