To provide a process for producing a seaweed vinegar sufficiently containing the seaweed components and keeping the characteristic taste and flavor of seaweed.

This seaweed vinegar can be produced by decomposing a raw seaweed such as tangle, sea mustard and hizikia with a phosphate agent or an organic acid salt to produce a seaweed extract liquid usable as a main raw material liquid for acetic acid fermentation, adding ethanol and a seed vinegar to the liquid and subjecting the mixture to acetic acid fermentation.