Parallax scrolling technique is being devoted as a unique and an innovative trend in the web design. Parallax scrolling provides 3D perception on a web page. Previous works observed user experience issues of parallax scrolling merely based on subjective questionnaires. Their findings leave a research question whether the results are valid, as participants may perceive a written questionnaire differently. Additionally, bias and ambiguity in the questionnaire can affect the research results significantly. To solve this research problem, we present a novel user experience study of parallax scrolling in storytelling and online shop website using eye tracking and User Experience Questionnaire (UEQ). Forty (N=40) participant joined the experiment on a voluntary basis. Each participant only interacted with one out of two websites (storytelling or online shop) and only one effect (with or without parallax scrolling). We found that parallax scrolling affected UEQ score of Attractiveness of the storytelling website (p < 0.05). Our findings suggest that parallax scrolling improves user engagement in storytelling website. We also observed that the participants spent time almost two times faster to find an object of interest in an online shop with parallax scrolling compared with the similar task in an online shop without parallax scrolling (p < 0.05). We thus argue that parallax scrolling is useful during interacting with particular websites that require visual object localization. In future, web designers should consider the appropriate usage of parallax scrolling to optimize user experience while avoiding additional distraction caused by this technique.