A locking device for a rod, that is configured to lock a rod movable rectilinearly in an axis direction at a stop position, the locking device (1A, 1B, 1C) comprising: multiple locking units that are configured to be arrayed along the rod and connected to each other, wherein the locking units each have an individual casing through which the rod is insertable and a lid that covers the casing, the casing accommodates a locking member that is configured to clamp and thereby lock the rod and a release piston that is configured to unlock the locking member by receiving fluid pressure, a release pressure chamber is formed between the casings and the lid so as to apply the fluid pressure to the release piston; wherein the lids of the locking units - are formed as a single member lid elongated so as to cover all the casings of the locking units or - are alternatively provided as separate lids for the different locking units; wherein - a single release port that is configured to supply and discharge a pressurized fluid and communication channels that communicate the release port with the respective release pressure chambers are formed in the single member lid or - alternatively a release port that is configured to supply and discharge a pressurized fluid and a communication channel that communicates the release port with the release pressure chamber are formed at each one of the separate lids; and wherein a ring-like connection spacer is disposed between the casings of adjacent locking units and is configured to be concentric with the rod, the connection spacer connects the casings of the adjacent locking units with each other, and the rod is insertable through a center hole of the connection spacer. multiple locking units that are configured to be arrayed along the rod and connected to each other, wherein the locking units each have an individual casing through which the rod is insertable and a lid that covers the casing, the casing accommodates a locking member that is configured to clamp and thereby lock the rod and a release piston that is configured to unlock the locking member by receiving fluid pressure, a release pressure chamber is formed between the casings and the lid so as to apply the fluid pressure to the release piston; wherein the lids of the locking units - are formed as a single member lid elongated so as to cover all the casings of the locking units or - are alternatively provided as separate lids for the different locking units; wherein - a single release port that is configured to supply and discharge a pressurized fluid and communication channels that communicate the release port with the respective release pressure chambers are formed in the single member lid or - alternatively a release port that is configured to supply and discharge a pressurized fluid and a communication channel that communicates the release port with the release pressure chamber are formed at each one of the separate lids; and wherein - are formed as a single member lid elongated so as to cover all the casings of the locking units or - are alternatively provided as separate lids for the different locking units; wherein - a single release port that is configured to supply and discharge a pressurized fluid and communication channels that communicate the release port with the respective release pressure chambers are formed in the single member lid or - alternatively a release port that is configured to supply and discharge a pressurized fluid and a communication channel that communicates the release port with the release pressure chamber are formed at each one of the separate lids; a ring-like connection spacer is disposed between the casings of adjacent locking units and is configured to be concentric with the rod, the connection spacer connects the casings of the adjacent locking units with each other, and the rod is insertable through a center hole of the connection spacer.