A hand held apparatus for curing materials with radiation of predetermined wavelength is disclosed. The apparatus includes a housing, a heat sink installed in the housing, a light emitting unit installed on the heat sink, the light emitting unit includes at least one light emitting element, a replaceable heat-dissipating module contacting the heat sink, and a light transmission unit coupled to the housing. The replaceable heat-dissipating module contains liquid for absorbing heat generated from the light emitting unit. The light transmission u nit is used for transmitting the radiation of the light emitting element to the materials. Whereby, the heat dissipation efficiency can be improved.