The present invention relates to an antihypertensiveagent including a boysenberry seed extract as an activeingredient. According to the invention, there can be providedan effective and highly safe antihypertensive agent havingantihypertensive effect so that the agent can contribute to theprevention and amelioration of hypertension and having verylittle risk of side effects even in continuous intake, and amethod for producing the antihypertensive agent at low costand efficiently.