  We have performed a series of cosmic-ray electron observations using the
balloon-borne emulsion chambers since 1968. While we previously reported the
results from subsets of the exposures, the final results of the total exposures
up to 2001 are presented here. Our successive experiments have yielded the
total exposure of 8.19 m^2 sr day at the altitudes of 4.0 - 9.4 g/cm^2. The
performance of the emulsion chambers was examined by accelerator beam tests and
Monte-Carlo simulations, and the on-board calibrations were carried out by
using the flight data. In this work we present the cosmic-ray electron spectrum
in the energy range from 30 GeV to 3 TeV at the top of the atmosphere, which is
well represented by a power-law function with an index of -3.28+-0.10. The
observed data can be also interpreted in terms of diffusive propagation models.
The evidence of cosmic-ray electrons up to 3 TeV suggests the existence of
cosmic-ray electron sources at distances within ~1 kpc and times within ~1x10^5
yr ago.

High Energy Astrophysical Phenomena