How to insert data to database with Laravel

i try to insert my data to database from form.

my url to create the data is web.com/siswa/create

but when i klik submit system show error MethodNotAllowedHttpException.

how i can fix it? is there anything wrong with my code?

here my form

<form action="" method="POST">
      <div class="form-group">
         <label for="exampleInputEmail1">NISN</label>
          <input type="text" class="form-control" name="nisn" id="nisn" placeholder="NISN"></div>
         <div class="form-group">
         <label for="exampleInputEmail1">Nama Siswa</label>
         <input type="text" class="form-control" name="nama_siswa" id="nama_siswa" placeholder="Nama Siswa"> </div>
         <button type="submit" class="btn btn-success btn-sm font-weight-bold">Submit</button></form>

my controller SiswaController

public function tambah()
    {
      return view('siswa.create');
    }

    public function store(Request $request)
      {

        $siswa = new \App\Siswa;
        $siswa->nisn = $request->nisn;
        $siswa->nama_siswa = $request->nama_siswa;
        $siswa->tanggal_lahir = $request->tanggal_lahir;
        $siswa->jenis_kelamin = $request->jenis_kelamin;
        $siswa->save();
        return redirect('siswa');
      }

and the last my route

Route::get('/siswa/create', [
    'uses' => 'SiswaController@tambah',
    'as' => 'tambah_siswa'
]);

Route::get('/siswa', [
    'uses' => 'SiswaController@store',
    'as' => 'simpan_siswa'
]);

via Chebli Mohamed