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We address the infrared(IR) divergence problem during inflation that appearsin the loop corrections to the primordial perturbations. In our previous paper,we claimed that, at least in single field models, the IR divergence isoriginating from the gauge artifact. Namely, diverging IR corrections shouldnot appear in genuine gauge-invariant observables. We propose here one simplebut explicit example of such gauge-invariant quantities. Then, we explicitlycalculate such a quantity to find that the IR divergence is absent at theleading order in the slow-roll approximation for the usual scale invariantvacuum state. At the same time we notice that there is a subtle issue on thegauge-invariance in how to specify the initial vacuum state.

IR divergence does not affect the gauge-invariant curvature perturbation