The purpose of focus-on-form instruction is to attract learners' attention effectively to linguistic forms of the target language during a meaning-focused activity. However, there is always competition of learners' attention between to form and meaning due to the fact that human attentional resources are limited. Task difficulty is identified asa critical factor which depletes learners' attention during language activities by many researchers. The purpose of the present study is to examine how task difficulty affects the allocation of learners' attention between form and meaning during different types of focus-on-form instruction, which are Textual input enhancement and Dictogloss. The results showed that learners' attention to form during the instruction was not affected by the task difficulty, while their attention to meaning was negatively affected by it. it means that focus-on-form instruction needs to be designed appropriately based on learners' level of language proficiency in order for it not to be focus-on-formS instruction which focus only on linguistic forms separately from meaning.