This work presents the psychometric properties of the Social Anxiety Questionnaire for Adults (SAQ-A30) with university students and analyses the differences and similarities in social anxiety in the sample. The 15,504 participants, students of 20 degree subjects in 17 Spanish Autonomous Community regions, were applied the SAQ-A30 and the “Liebowitz Social Anxiety Scale-Self Report” (LSAS-SR). A five-factor structure was obtained through several factor analyses as well as an exploratory structural equation modeling of the SAQ-A30: “Speaking in public/Talking with people in authority”, “Interactions with strangers”, “Interactions with the opposite sex”, “Assertive expression of annoyance, disgust or displeasure”, and “Criticism and embarrassment”. Internal consistency was 0.91 and concurrent validity (paired with LSAS-SR) was 0.66. Significant differences were found between males and females, but there was scarce difference between regions and subjects studied. These results confirm the five-factor structure and the good psychometric characteristics of the SAQ-A30, which make it a suitable instrument for assessing both general and specific social anxiety in universities, taking into account sex differences.