To provide a photocatalyst unit improved in the decomposition efficiency of a harmful gas by increasing the contact efficiency of the harmful gas with the photocatalyst even if a sheet like photocatalyst convenient in mass production or handling is used and a harmful gas removing device using the unit.

The photocatalyst unit 11 is composed of the photocatalyst sheet 3 formed by immobilizing the powdery photocatalyst with a binder sheet- likely at least on one main surface and a supporting member 1 for supporting the sheet, the supporting member 1 is provided with an opening part 6 for bringing the immobilized photocatalyst into contact with a gas to be treated and a turbulence imparting member, e.g. a rod member 2 for generating turbulence in the flow G of the gas to be treated. The harmful gas treating device is provided with a photocatalyst module formed by arranging a plurality of photocatalyst units 11 in a module frame and a lamp module, in which a light source for exciting the photocatalyst is incorporated.