We address the localization of a scalar field, whose bulk-mass M is considered in a wide range including the tachyonic region, on a three-brane. The brane with non-zero cosmological constant λ is embedded in five dimensional bulk space. We find in this case that the trapped scalar could have mass m which has an upper bound and expressed as m = m20 + αM 2 ≤ β|λ| with the calculable numbers m20, ...