We propose a desk-side supercomputer with large-scale reconfigurable data-paths (LSRDPs) using superconducting rapid singleflux-quantum (RSFQ) circuits. It has several sets of computing unit which consists of a general-purpose microprocessor, an LSRDP and a memory. An LSRDP consists of a lot of e.g, a few thousand, floating-point units (FPUs) and operand routing networks (ORNs) which connect the FPUs. We reconfigure the LSRDP to fit a computation, i.e., a group of floating-point operations, which appears in a 'for' loop of numerical programs by setting the route in ORNs before the execution of the loop. We propose to implement the LSRDPs by RSFQ circuits. The processors and the memories can be implemented by semiconductor technology. We expect that a 10 TFLOPS supercomputer, as well as a refrigerating engine, will be housed in a desk-side rack, using a near-future RSFQ process technology, such as 0.35 mu m process.