A transformer, comprising: an uncut magnetic core (5,15,20,25,33) formed by winding or layering a magnetic alloy ribbon, the uncut magnetic core (5,15,20,25,33) forming a closed magnetic path; a protector member covering at least part of the magnetic core (5,15,20,25,33); a primary coil (2,12,16,21,31) and a secondary coil (3,13,17,22,32); and at least one bobbin (4,14,18,19,23,24,30) around which a lead wire which forms the primary coil (2,12,16,21,31) and the secondary coil (3,13,17,22,32) is to be wound, wherein the at least one bobbin (4,14,18,19,23,24,30) includes a cylindrical portion which has a circumferential surface around which the lead wire is to be wound, a pair of flanges arranged so as to sandwich the circumferential surface is located in an axial direction of the cylindrical portion, and at least one gear portion provided on an outer side of at least one of the pair of flanges so as to be spaced away from the flange, the at least one bobbin (4,14,18,19,23,24,30) being attached so as to be rotatable around the protector member at the cylindrical portion, at least one of the pair of flanges has a lead wire passage portion that is provided on an outer side of the flanges, and an end portion of the lead wire is wound around the circumferential surface of the cylindrical portion, the lead wire passage portion includes a pair of recesses which are arranged so as to sandwich the cylindrical portion when seen in an axial direction of the cylindrical portion and which allow passage of the lead wire at a position radially inner than an outer circumferential edge of the flanges, a wound portion of the lead wire which forms the primary coil (2,12,16,21,31) and a wound portion of the lead wire which forms the secondary coil (3,13,17,22,32) are arranged alternately in a radial direction of the cylindrical portion, lead wire portions of respective ones of a plurality of wound portions of the lead wire which forms the primary coil (2,12,16,21,31) which overlaps via a wound portion of the lead wire which forms the secondary coil (3,13,17,22,32) are connected in parallel on an outer side of the flanges, and lead wire portions of respective ones of a plurality of wound portions of the lead wire which forms the secondary coil (3,13,17,22,32) which overlaps via a wound portion of the lead wire which forms the primary coil (2,12,16,21,31) are connected in parallel on an outer side of the flanges, and an end portion of the lead wire which forms the primary coil (2,12,16,21,31) is provided on an outer side of the flanges via one of the pair of recesses, and an end portion of the lead wire which forms the secondary coil (3,13,17,22,32) is provided on an outer side of the flanges via the other one of the pair of recesses. an uncut magnetic core (5,15,20,25,33) formed by winding or layering a magnetic alloy ribbon, the uncut magnetic core (5,15,20,25,33) forming a closed magnetic path; a protector member covering at least part of the magnetic core (5,15,20,25,33); a primary coil (2,12,16,21,31) and a secondary coil (3,13,17,22,32); and at least one bobbin (4,14,18,19,23,24,30) around which a lead wire which forms the primary coil (2,12,16,21,31) and the secondary coil (3,13,17,22,32) is to be wound, wherein the at least one bobbin (4,14,18,19,23,24,30) includes a cylindrical portion which has a circumferential surface around which the lead wire is to be wound, a pair of flanges arranged so as to sandwich the circumferential surface is located in an axial direction of the cylindrical portion, and at least one gear portion provided on an outer side of at least one of the pair of flanges so as to be spaced away from the flange, the at least one bobbin (4,14,18,19,23,24,30) being attached so as to be rotatable around the protector member at the cylindrical portion, at least one of the pair of flanges has a lead wire passage portion that is provided on an outer side of the flanges, and an end portion of the lead wire is wound around the circumferential surface of the cylindrical portion, the lead wire passage portion includes a pair of recesses which are arranged so as to sandwich the cylindrical portion when seen in an axial direction of the cylindrical portion and which allow passage of the lead wire at a position radially inner than an outer circumferential edge of the flanges, a wound portion of the lead wire which forms the primary coil (2,12,16,21,31) and a wound portion of the lead wire which forms the secondary coil (3,13,17,22,32) are arranged alternately in a radial direction of the cylindrical portion, lead wire portions of respective ones of a plurality of wound portions of the lead wire which forms the primary coil (2,12,16,21,31) which overlaps via a wound portion of the lead wire which forms the secondary coil (3,13,17,22,32) are connected in parallel on an outer side of the flanges, and lead wire portions of respective ones of a plurality of wound portions of the lead wire which forms the secondary coil (3,13,17,22,32) which overlaps via a wound portion of the lead wire which forms the primary coil (2,12,16,21,31) are connected in parallel on an outer side of the flanges, and an end portion of the lead wire which forms the primary coil (2,12,16,21,31) is provided on an outer side of the flanges via one of the pair of recesses, and an end portion of the lead wire which forms the secondary coil (3,13,17,22,32) is provided on an outer side of the flanges via the other one of the pair of recesses.