Tc1/mariner superfamily transposons are used as transformation vectors in various model organisms. The utility of this transposon family is evidenced by the fact that Tc1/mariner transposons have loose host specificity. However, the activity of these transposons has been observed in only a few organisms, and a recent study in the ascidian Ciona intestinalis suggests that not all Tc1/ mariner transposons show loose host specificity. To understand host specificity, we used sea urchins, since they have a long history as materials of embryology and developmental biology. Transposon techniques have not been reported in this organism, despite the likelihood that these techniques would open up many experimental possibilities. Here we tested the activity of three Tc1/ mariner transposons (Minos, Sleeping Beauty, and Frog Prince) in the sea urchin Hemicentrotus pulcherrimus. Minos has both excision and transposition activity in H. pulcherrimus embryos, whereas no excision activity was detected for Sleeping Beauty or Frog Prince. This study suggests that Minos is active in a broad range of non-host organisms and can be used as a transformation tool in sea urchin embryos.