  The lightest Kaluza-Klein particle (LKP), which appears in the theory of
universal extra dimensions, is one of good candidates for cold dark matter
(CDM). When LKP pairs annihilate around the center of the Galaxy where CDM is
concentrated, there are some modes which produce electrons and positrons as
final products, and we categorize them into two components. One of them is the
"Line" component, which directly annihilates into electron--positron pair.
Another one is the "Continuum" component, which consists of secondarily
produced electrons and positrons via some decay modes. Before reaching Earth,
directions of electrons and positrons are randomized by the Galactic magnetic
field, and their energies are reduced by energy loss mechanisms. We assume the
LKP is in the mass range from 300 GeV to 1500 GeV. We calculate the electron
plus positron spectrum after propagation in the Galactic halo to Earth, and we
analyze the resulting spectrum and positron fraction. We also point out that
the energy dependence of observed positron fraction is well reproduced by the
mixture of "line" and "continuum" components. We can fit the electron plus
positron spectrum and the positron fraction by assuming appropriate boost
factors describing dark matter concentration in the Galactic halo. However, it
is difficult to explain both the electron plus positron spectrum and the
positron fraction by a single boost factor, if we take account of observational
data obtained by AMS-02 only.
