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A search for solar axions has been performed using an axion helioscope which is equipped with a 2.3 m-long 4 T superconducting magnet, PIN-photodiode X-ray detectors, and a telescope mount mechanism to track the sun. In addition, a gas container to hold dispersion-matching gas has been developed and a mass region up to m a = 0.27 eV was newly explored. From the absence of any evidence, analysis sets a limit on axion-photon coupling constant to be g aγγ < 6.8-10.9 × 10 −10 GeV −1 for the axion mass of 0.05 < m a < 0.27 eV at 95% confidence level, which is more stringent than the limit inferred from the solar-age consideration. This result gives currently the most stringent observational limit on the existence of solar axions in this mass region.

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