Abstract. -We propose a new stage of confiment-decofinment transition, which can be observed in laboratory. In two-gap superconductors (SCs), two kinds of vortex exist and each of them carries a continuously variable fraction of the unit flux quanta Φ0 = hc/2e. The confined state of these two is a usual vortex and stable in the low temperature region of the system under a certain magnetic field above Hc1. We see an analogy to quarks in a charged pion. An entropy gain causes two fractional vortices to be deconfined above a certain temperature.Introduction. -Topological defects furnish fascinating problems in physics, and keep attracting a lot of concerns. In general, they lead the quantization of physical quantities. Vortex is one of the most important example of topological defects [1]. It is well known that in superconductors (SCs), the requirement that the order parameter is a single-valued function guarantees the quantization of the magnetic flux of a vortex in the unit of Φ 0 = hc/2e.The fractionalization of topologically quantized numbers have also been researched extensively in many different contexts [2]. Vortices with fractional fluxes have been discussed in p-wave superfluid Here we discuss vortex state in two-gap SCs [6] which has two superconducting gaps on two separate Fermi surfaces. The two-gap superconductivity can be seen in a lot of SCs in solid state and has been paid special attention. MgB 2 is a recent typical textbook [7]. The possibility of the two-gap superconducting state is also pointed out in 2H-NbSe 2 [8], PrOs 4 Sb 12 [9], Y 2 C 3 [10], Ca-doped YBCO [11], and liquid hydrogen [12]. The fractionalization of the flux quanta has also been discussed in two-gap SCs [13,14]. Tanaka considered a wire ring and showed that a trapped flux in the ring can be an arbitrary fraction of Φ 0 [13]. Babaev considered a planer geometry and dis-

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