The purpose of this study was to investigate muscle activity of the lower limbs when walking in jeans in order to obtain basic information for development of new jeans patterns with excellent movement adaptability. Using three types of jeans (basic, medium, and slim) with different ease on hip, knee circumference, and crotch length, and two different types of shoes, Electromyogram (EMG) of the lower limbs muscle was measured for four healthy subjects walking on treadmills and stairs. EMG of vastus lateralis, semitendinous, tibialis anterior and medial head of gastrocnemius muscles was measured. The muscle activity was assessed in RMS (Root Mean Square) value of the EMG. On the treadmill in sneakers, only the vastus lateralis muscle showed a significant difference in RMS value depending on patterns. Basic and medium jeans allowed higher muscle activity than trunks of slim jeans did. On the treadmill in high heels and slim jeans, the RMS values of all muscles were significantly smaller than in basic jeans, whereas no significant differences were shown while in trunks or medium jeans. On the stairs either in sneakers or in high heels, no significant differences were shown between all muscle activities for all types of jeans. On the treadmill, greater fatigue was induced in all muscles from walking in high heels than in sneakers for all jeans patterns. When walking on the stairs wearing either type of shoes, however, the effect of jeans pattern on muscle activities was different from muscle to muscle.