A trimmer includes a working head having a housing and a handle that extends outwardly from a rear end of the housing, at least one wheel mounted on the rear end of the housing, a support element for supporting the working head that is located below the housing and mounted on the housing through a shaft, a cutting element coupled to the housing coaxial with the support element, and a cutting height adjustment device which is respectively connected with the at least one wheel and the shaft for adjusting a cutting height of the trimmer via movement of the at least one wheel and the shaft to which the support element is coupled relative to the cutting element. In this manner, no matter the cutting height, a cutting surface of the cutting element can be ensured to be substantially parallel to the ground.