An object of the present invention is to preserve the total content of chlorophyll in an extract while increasing the extraction yield of a Spirulina extract. Another object of the present invention is to provide a pharmaceutical composition and health functional food for prevention or treatment of degenerative cranial nerve diseases containing a Spirulina extract as an active ingredient, and to provide a method for treating degenerative cranial nerve diseases using a Spirulina extract. The present invention provides a method for producing a Spirulina extract including the steps of (a) preparing a Spirulina powder; (b) adding 50% to 80% of ethanol to the Spirulina powder and performing an ultrasonic pretreatment at 15° C. to 35° C.; (c) extracting a Spirulina extract at 50° C. to 80° C.; (d) vacuum-concentrating the Spirulina extract; and (e) freeze-drying the vacuum-concentrated Spirulina extract.