This study was conducted to provide fundamental information necessary to solve use conflict problem between hikers and mountain bikers though understanding the present state of use conflict and its possible causes. Data were collected from a total of 2,075 hikers and mountain bikers who visited Mudeungsan Provincial Park(MPP) and Samgaksan area through questionnaire survey and in-depth (or field) interview. This study worked for seven major themes and the study results of each theme are as follows. 1) 30.2% of the respondents saw or encountered mountain bikers in MPP (avg: 1.7 times/day). 77.1% of the respondents thought that mountain biking activity in MPP causes problem, and 73.5-83.2% of the respondents perceived conflict by mountain bikers' problematic behaviors. 2) Hikers' perceived conflict (mean: 3.03) by mountain bikers was higher than vise versa (mean: 2.35). A survey using a series of simulated photographs (modifying number of hikers/mountain bikers) also showed that hikers perceived conflict more . Mountain bikers perceived that hikers encounter more mountain bikers' problematic behaviors than they actually did. 3) Hikers of Samgaksan area perceived more conflict than hikers of MPP. Generally, there were no differences in perceived conflict by number of mountain bikers and hikers' group size between MPP and Samgaksan area. 4) While hikers preferred 'beautiful landscape/nature,' 'steps/many hikers,' and 'many trees/quietness' than mountain bikers, mountain bikers preferred 'trail covered with asphalt or concrete'. Especially mountain bikers didn't like steps in trail. 5) Hikers evaluated that mountain bikers' manner (mean: 3.69) and riding speed (mean: 3.57) was the most influential factors to their recreational experiences. 6) A field experiment showed no differences between three experimental groups (Control: 0 mountain biker, Low: 1 and 3 mountain bikers, High: 5 and 7 mountain bikers). As the number of mountain bikers increased, hikers' perceived number of mountain bikers also increased. 7) A qualitative research method (in-depth interview and field interview) was used to identify causes of use conflict. Based on the collected data, the major causes of use conflict were classified into 'differences in ways of achieving recreational goals,' 'safety,' 'mountain bikers' manner,' 'inconvenience of using trail,' 'disharmony,' 'equity (vested rights) in using places'. Possibility of deteriorating trails due to mountain biking didn't influence hikers' perceived conflict.