The invention relates to the field of building operations, in particular to a concrete-structured conjoined cylindrical shell construction device and a method therefor. The construction device comprises a
pulley (1), a run derrick (2), a reinforced hoop (3), a steel
wire rope (4), a chain hoist (5), a
handrail (6), a radial spar (7), a platform ring beam (8), a
safety net (9), an external hanger frame (10), an inner form spreader (12), a stay bar pivot ring half-way line frame (13), an operation platform (14), an external die plate (15), an internal die plate (16), a rigid axis connector (17), an internal hanger frame (18) and a
diameter-adjusting screw (19). The construction method comprises the installation of the run derrick, the operation platform, the external die plate and the internal die plate, the construction of concrete, the normal die construction and connection of silos, which are conducted in sequence. The invention features simple operation, shortened construction period and lowered construction cost.