\documentclass{article}
\usepackage{tikz}

\usetikzlibrary{shapes, positioning}

\begin{document}

\begin{tikzpicture}[node distance=2.3cm, auto]
    \node (start) [circle, draw] {Start};
    \node (process1) [right of=start, rectangle, draw] {Process 1};
    \node (decision) [right of=process1, diamond, draw] {Decision};
    \node (process2a) [below of=decision, rectangle, draw] {Process 2a};
    \node (process2b) [right of=decision, rectangle, draw] {Process 2b};
    \node (end) [right of=process2b, circle, draw] {End};
    \draw[->] (start) -- (process1);
    \draw[->] (process1) -- (decision);
    \draw[->] (decision) -- node {yes} (process2b);
    \draw[->] (decision) -- node {no} (process2a);
    \draw[->] (process2a) -| (process1);
    \draw[->] (process2b) -- (end);
\end{tikzpicture}

\end{document}