PURPOSE: To enable a shift to be safely carried out by monitoring the attitude of a caisson under shifting at all times, and thereby constituting the device to quickly provide warning visually and audibly when the attitude of the caisson is found to have been abnormal beyond a condition which is inputted into a monitor section in advance.

CONSTITUTION: An ultra sonic wave water gauge 4 is installed onto the rear end of a horizontal stem 3C in such a way that it acts downward, and a data transmitting section 5 is also installed onto the upper end of a pillar 3B in such a way that it acts forward. Before a shift is started, the dimensions of a caisson a warning condition, a reference water level and the like are inputted as initial set values into a processing unit 10. While the shift is carried out, the A/D conversion of measured data from the ultra sonic wave water gauge 4 and an inclination detecting section 6 is made, and the resultant is transmitted by wireless to a data receiving section 9 by a data transmitting section 5. Measured data thus transmitted is compared with data on the dimensions of the caisson, the warning condition, the reference water level and the like which are inputted as the initial set values by the processing means 10, so as to be operated, so that attitude information such as freeboard, the inclination and the like is thereby displayed over a screen 10A attached to the processing means 10.