A hydrogen generator associated with the invention comprises a hydro-desulfurizer (1) configured to remove sulfur compounds from a raw material; a reformer (2) configured to generate hydrogen-containing gas with use of the raw material that has passed through the hydro-desulfurizer (1); a raw material supply device (3) configured to supply the raw material to the reformer (2); a recycle flow passage (4) configured to supply a portion of the hydrogen-containing gas, discharged from the reformer (2), to the raw material before the raw material flows into the hydro-desulfurizer (1); an on-off valve (5) provided in the recycle flow passage (4); a pressure detector (6) located at a position upstream of the on-off valve (5) in the recycle flow passage (4); and an abnormality detector (7) configured to detect an abnormal clogging in the recycle flow passage (4) based on a pressure detected by the pressure detector (6), in a state in which the raw material supply device (3) is supplying the raw material to the reformer, (2) with the on-off valve (5) closed.
